Found this website where the author explains how things were run in Vietnam. On a very, very basic level, for people who wanted to write a novel set over there.
Again, I have to stress that this is at a very basic level. But it gives good hints, and if you want to go deep diving you can easily go further. (
Topics covered include: How recreation worked, where were the women, how the different 'social classes' in the corps interacted with each other (or not)
TOD - Tour of Duty - Writing about believable combat
Basic description of a stint in Vietnam