Well you'll want to get the latest patch it fixes many bugs, gives you Gem Editor, makes the game easier and allows you to do The American Campaign at the start instead of having to do The NVA one first, here's a link to the page (It's direct from the company so don't worry).
http://www.menofwargame.com/support
Make sure it's on the Men Of War Vietnam section and pick the "Patch 2" (if your in germany then you'll have to pick the patch specifically for the germans it'll be in brackets).
Any problems PM me and I'll try and help you out.