Quick question.
On the SF mission, how do you 'use' the truck? I did the whole mission up to that point, got to the truck and a message flashed up saying 'Use the Truck'. I pressed some random buttons and a helicopter appeared. I went underneath the chopper but I was still getting the 'Use the truck' message so I went back to the truck and pressed some more random buttons. One of them unfortunately was the escape key which sent me back to the training list meaning I had to start again....
Quick couple of points for the rest of the mission though.
To get to Objective B drop into the gully at the bridge and go LEFT instead of right, it's much easier this way. Sneak down there, as long as you stay low you can pretty much ignore the watchtowers on the way. More or less opposite the third one you pass (including the one right by the first bridge) is a tree and some rocks on your right. Behind the tree is a narrow path which leads over the hill and brings you out behind a mess tent.
Stay against the rocks and sneak past the guard sat at the table - as long as you make no noise he won't spot you.
You then come to a rocky outcrop. Go right, through the narrow valley rather than around the top to the left and just follow the compass to objective B.
To get past the initial searchlight on the way to objective C, I tried the methods given earlier and got spotted every single time.
Eventually I tried this and it's worked every time for me so far.
Crawl up on the right side of the valley as close as you can get to the nearest swing of the searchlight. Position yourself so it gets as close as possible to you without revealing you. As it swings away, fast crawl up behind it being careful not to catch up with it and get caught in the light. When it gets to the end of the swing, fast crawl to the rocks on the left and the searchlight should swing past behind you and the guard on the opposite hill won't spot you.
Another tip for getting into the gullies without falling and standing up. Crawl in very slowly at an angle to the slope. Inch forwards a bit at a time and if you get it right you'll slide slowly down the slope. Stop moving when that happens and let gravity work. When you stop, if you're not at the bottom, inch forwards again until you slip the rest of the way.