This area unfortunately does not have a map, but it's pretty linear, so hopefully you shouldn't have any problems finding your way. I have constructed a map, however, and added some "landmarks," so hopefully it'll help in case you get stuck, or otherwise lose your bearings.
For the most part, the facility is deserted with the exception of about three Bloodsuckers - so you should be able to proceed fairly quickly until you reach the deactivation mechanism for the Brain Scorcher. Once you turn off the Brain Scorcher though, getting out wont be as easy as it was getting in.
During your way through the "lab" you'll come across three doors with a keypad next to them. Only one of the doors (#2) will actually have something interesting behind it - the two others has a wall and a small empty room behind them, respectively. Refer to the text below for the code for door #2.
Your starting point is on the top floor, at the southern part of the facility. You're likely to come upon a number of metal and wooden boxes, so be sure to break them to find goodies. When you move forward to the north you'll see a partially shut door in front of you - you can't go through, so head west, down the ramp and into the hallway going north. You'll soon come to a small room with a pool and a shaft in it, proceed through, going west and then north. You'll come to a room with a round "tank" (or some such) in the middle, and beyond that a larger room with three pumps (or something along those lines) in it; to the south you can find a small room with a locked door and a keypad next to it (this is keypad door #1 on the map). Unfortunately, I have never discovered a code to open it so I am not sure if there actually is something on the other side (you pass the other side of this door further on - PinothyJ). Anyway, since this is a dead end, head north, up the stairs, into the hallway that is initially going west and soon turning north; at the end of the hallway is a large room, which has the first Bloodsucker in it. There is a metal box ,just inside the doorway (behind a metal grating), here with some 9x39mm ammo, a scientific first aid kit and an anti-rad inside it. You may also be able to find some artifacts and a F1 Grenade near the south-western corner of the room. In the next room you can go both north and south - going north though will take you to a small room it has a metal box sitting on a shelf, so break that and take the goodies - more 9x39 mm ammo and another scientific first aid kit. Move south into the hallway and then west towards another large room. This room has what appears to be a freight elevator in the middle. In the south-eastern part of the room you can find the stairs moving down to the bottom floor - before you head down, you may wish to explore the southern part of the top floor - you'll come upon two large rooms with some boxes in them.
Moving down to the bottom floor, you'll come upon a medium sized room that has yet another locked door and a keypad in it (this is keypad door #2 on the map) - you may have found the code to the door on Monolith soldiers, but don't despair if you haven't - the code to the door is 342089. Inside you'll find a number of medkits, along with some 5.56x45mm AP rounds sitting on the table and a few F1 grenades underneath. Moving on, head west into the hallway and follow it - you'll soon see it open towards the north and south. It's a dead end to the north, but to the south you'll see a large room with two parallel walls inside it. This room has another Bloodsucker inside (or near) it, so deal with the mutant and head west. The third Bloodsucker is in a room up ahead - but it may have heard you deal with the second one, so proceed with caution.
You'll reach a small room with three alcoves in it - there may be boxes here, so break them and pick up any interesting items you may find. Move north and then west, up the stairs, and then north again. You'll come to a room with a ladder and another shaft in it. In the following room you can find a metal box sitting on a shelf - it has some goodies inside it. Moving on towards the north you'll come to a room with some sort of machinery in it; behind it you can see some metal grating as well as the exit. Continue on, moving east, up the stairs and into a large room with some ledges and ladders in it. Continue east, through series of three almost identical rooms. In the final room to the east, you can find some stairs going up to a walkway. Head up there, into the hallway and you'll come to the final room - the mechanism for shutting down the Brain Scorcher. The switch is one the console west of the marker on your mini-map. The room also has another locked door with a keypad next to it - but alas, I think this is again a door you wont be able to open, I've never found the code for it myself. Activate the switch and you'll - surprise, surprise - pass out and be treated to another cut-scene.
Once you wake up you'll notice that your mini-map has picked up about 20 PDAs - in other words, you got company, and they're not here to chat, either.
You now have to escape from the facility. As stated above, you'll have to deal with a lot of enemies, Monolith soldiers specifically. Depending on what type of armour and weapon(s) you brought, getting out can be tricky since you'll be facing an armed and armoured opposition - they'll be using anything from Akms up to TRs-301 and GP-37 rifles, and some of them will be wearing Exoskeleton armour. Fortunately all of the Monolith guys are scattered all over the bottom and top floor, so you won't have to go up against that many at a time. Before you proceed, you should maximise your bullet-proof cap by wearing any appropriate artifacts that you may have.
The first enemy is located in the last of the three identical rooms, and there is another soldier in the room next to it. The next batch of soldiers is in the large room to the west - some may be located upon the upper walkways, so make sure you lean out and check for soldiers in all directions.
In the upcoming hallways you may wish to use some of your grenades, which you are likely to have plenty of by now - they can be especially useful for clearing the way or just flushing out soldiers. Slowly but surely you should be able to make your way back to the entrance. If you use a silenced weapon, such as the Vintar BC, most of the soldiers won't even know that you're coming and will simply stand guard - which makes them quite easy to take down.
Once you're at the entrance and head back into the Red Forest you'll hear a transmission from the military. They have moved in on the perimeter, as have some lone stalkers, so when you move back towards the train car, you're likely to see a large fire-fight going on. Use the fact that both the military and the Monolith will be focused on each other and the lone stalkers.
Wait for the combat to finish outside. If you use an unsilenced weapon, or throw some grenades, you'll likely come under the attention of the remaining military soldiers. The train car can be an excellent spot to use as a choke point, since most, if not all, of the soldiers will come to you. Once you've disposed of them, head to into the outer facility and make your way back.
Now that you have disabled the Brain Scorcher, the road to the north going into Pripyat is now open, and as the Barkeep informs you, it seems that everyone is heading towards the centre of the Zone. He also informs you that a group of stalkers are gathering in Pripyat and are going to try to reach the centre of the Zone - and that you can group up with them if you make haste. No need to hurry though, since they'll basically be waiting for you to arrive. I would definitely suggest that, before going to Pripyat, you head back to the Bar to replenish your ammo, and possibly to get new armour and weapons. Going to Pripyat is almost a guaranteed one-way ticket, so once you get there, you're not likely to come back.