If you want to spare you the bother, or just have a very very detailed workbase, someone here has just issued a pretty good Vietnam mod!
You can download the Viet War Pack 3.1 here:
http://rapidshare.de/files/2151698/V...k_3.1.zip.html
Probably you can find much more details on Vietnam-era USMC there than what was possible to put in the game!
Then either you are satisfied with this one or want to overdetail on top of it is your concern!
But I guess if you have feedback about this the author would be glad to hear it... Don't doubt he'll be here soon enough!