1. Gain entry to laboratory area: easy 
2. Contact double agent: easy,medium, hard 
3. Rendezvous with 006: easy, medium, hard 
4. Destroy all tanks in bottling room: easy, medium, hard 
5. Minimize scientist casualties: easy, medium, hard 

Head down the air shaft to the bathrooms, where you'll see the head of a sergeant. There are three other soldiers in this room. Kill them with your PP7, other soldiers will hear and swarm the bathroom. 

Leave the bathroom, but don't go downstairs. On that floor open up the door and at the bottom of the stairs is one guy. Kill him, and then open the door near to where he was standing. Open it, take a few steps, turn left and you'll be behind a guard with Keycard B, which will permit you into an important security room. Across from the stairs is a security door, open it and press B to activate the computer in front of you. There should be three guards in there, and now you should switch to your KF7. Make sure not to blow up the computer. This keycard will open up a timed security door down the hall and to the left. Be quick because there's yet a third door to run through and it closes fast. 

Leave that room, turn left, run down the hall, pick up the armor to your left, keep running, take your first left, and open the door on your left. Then turn right, and pass through that door and stop. To your left in a locker room are two guards, it's not necessary to kill them, but it's fun. Now open the next door, behind which at least three soldiers are waiting with rifles in hand. Open it, step back a few feet and wait for them to enter. They line up so the killing is easy. Go in and check the left and right rooms, where Dr. Doak, the double agent scientist, will hand you a door decoder for later use. He may not be there (he's got a light brown hair and a beard and he walks slow, without putting his hands up) -- if he's not there, you'll see him near the bottling facilities upstairs. 

Leave those two bottling rooms and continue on through the next door. In front of you is the room with the two security switches, and hallways on either side. Pull out your PP7; pick off the security guard to your left and right. Now, enter and go toward the room in front of you. The room is filled with four guards, so switch to your KF7, but don't throw a mine in there. Go to the left and right and pick off the guards. Almost guaranteed, you'll invite others. After dusting those stray guards, and facing the door, hit the console on the right with the flashing button, press B , and now run because the doors are timed. Of course, you'll have to bust out through about five guys, so reload your KF7 and then blow the guards away. 

If you make it through the security door, go up the stairs, dust the three to four guards and enter the bottling rooms, one by one, to find Dr. Doak, if you haven't already found him. He walks around, and may actually walk toward you if he's near. Talk to him, wait until you get the decoder key, and then get ready to run. Have your KF7 loaded and ready. Now run down the only other hallway. Killing about three guys should set you free for a few seconds. 

Now, you can use the door decoder. You'll see two doors, the one on the right is your door. In easy mode, you simply approach it, but in medium and hard you must switch to the key and wait. Once you're through it, switch to the mines. Go down the stairs, approach 006 so that a conversation begins and as soon as it starts lay one mine on each of the five giant vats. Across the room from the staircase you descended, there is a door -- it's your escape route. Now there are only two things that need be done. One, make sure that 006 is about 5-10 feet away from the tanks (so that when you blow them up he doesn't die). Two, blow up the ALL of the vats. As soon they're toast, just walk out that door. If you stick around to see what happens, guards will come by the bucketload hooting and a'hollering and gas will flood the room. Make it out alive, and your mission is accomplished.