The first section of the mission is a full-out firefight, so be prepared to do a LOT of shooting. You can sneak around to either side to get the drop on soldiers rather than taking them head-on. The next section is what Grim calls a maze. There are so many places to sneak and hide, barrels to shoot, pipes to hang from, you name it. Go nuts.
In the next section, look for a ladder to climb and a duct to go into. From there you can get the drop on unsuspecting engineers. There are two armored guys in here, and you can’t move on until you get all of them, so look in the corners. One of them is an HVT, too.
The next section is all platforming. Follow the marker and look for alternative routes. If you get stuck, look for a broken railing. Drop into the corner there and shimmy along to keep going. Then look for a pipe. The next section is more of the same until you reach the control room.
When you reach the bottom of the shaft, man up. There are freakin’ SIX armored guys coming. Grenades and mines are your friends. After that, there’s a running chase. There are a few guys along the way, but nothing you can’t handle by now.