It's definitely not the worst I've seen, but as said before, there is a bit too much orange. If you are giving it that color due to the explosion, I would only edit the lighting near the rocks and trees at the top of the hill. Also the explosion itself doesn't seem to have much depth. Trying to think of a way to fix that, but not really sure at the moment. Also, I've been wondering where everyone is getting those models, as I'd like to do a few Vietnam poses myself. Could you share a link perhaps?
i had some over dramatic "sky of fire" thing in mind with the orange, but now that i look at real pictures of explosions i noticed that when it's dark and there's an explosion you don't really get that at all. pretty messed up on my part
and about the models, i'd be happy to give you some links 
hueys and the patrol boat
http://www.facepunch.com/threads/111...-Destruction-2
the marines and some weapons and stuff
http://www.facepunch.com/threads/111...d-other-things
vietcong dudes
http://www.facepunch.com/threads/111...ietcong-Models