This mission is a lot like Protect the Gallimimus in graphics and layout, although it's shorter. In other words, it's cheesecake—except for one nasty bit we'll talk about in a minute. You have a time limit, but it's nothing too major. Don't dilly-dally, but you don't have to keep plunging ahead blindly.
You will encounter only Biosyn here, including the annoying flamethrowers. You can use the machine gun throughout the level, though in a few places you will want to take out flamethrowers using the shotgun. There is only one ammo pickup, but it doesn't terribly matter whether you pickup for the machine gun or the shotgun. You really don't need many shotgun shells, though, so you might prefer to pick it up for the machine gun.
Near the beginning of the level, a helicopter will appear above you and drop a few boxes. These are probably the supplies you're supposed to be waiting for. Don't worry, the boxes won't land on you. Toward the end of the level, there is a really nasty part where you will encounter a stack of two boxes with a flamethrower behind it, then behind him, a stack of three boxes with a grenadier on top. This is the hardest part of the level and you'll be fine once you get past it. The problem is the flamethrower's fire will go through the boxes, so it can hurt you, but the boxes stop your weapons dead. One way to handle this is to stand close, but not too close to the flames, careful to avoid the grenades, then when the flamethrower stops firing for a second, jump atop the boxes while firing the shotgun to dispatch the grenadier, then jump to where he was standing, and quickly jump to the ground, away from the flamethrower. (Whew!) It helps to have a lot of health at this part. You can also try to take out the grenadier while you're still in front of the two boxes, by jumping up and forward, firing, then quickly pulling away before you get scorched, repeating until the grenadier is dead. Then you won't have to worry about getting hit with a grenade when you're avoiding the flames. Whichever way you do it, it's tricky.