Red Section soldier: "I want into the server room. Now. Or I'll kill you myself."
Technician: "I can't... The locks are palm print readers... They don't work without power..."
Red Section soldier: "Then take me to the power room. You're going to restore the power."
When the elevator doors open, a pair of Red Section thugs will freak out and run from you. Let them do just that, and a wall of fire will set them ablaze. Snipe the switch at the far end to extinguish the flames. Go towards the next area, and snap to cover.
A gang of troops will assault you. One of them will even drop to your level so deal with him before taking on the stragglers. When they're dead, use the RTL to cross to the next side and get the Galil if you so wish. Climb the ladder and a cutscene will play.
Kill the duo inside the office, and then grab anything you need from them. Head down the stairs, but watch out for another pair that comes up. When they're down, a third group will attack. Kill them, and search this area for two vents you can shoot. Do so, and slowly head for the next area.
A shotgun-brandishing troop is forcing the electrician to restore the power. Spook the mercenary, and the civilian is as good as dead. Silently head for the power room, and push (DON'T KICK!) the door open at the far end. If you wish to, your taser will make a pretty funny death for the terrorist. Drop him, and the employee will ask a favour from you.
Hit the wall switches, and then pull the lever at the civilian's command. This will draw the mission to a close.
1: Directly in front of the elevator is the first file.
2: After using the RTL, to the left is another file.
3: Again, at the end of the RTL, search the right for the third file.