Ninja-san...
Recently someone here asked a similar question, and the answers will probably make you smile, as they hit all your bases for ya.
One was the Tamiya Panzer II -- a small but important tank. These little fellows would be all dark-grey, or all desert yellow if in North Africa. I remember building this kit as a teen (haven't build it in years), and it goes together well and quickly. A satisfying little project.
The other one recommended was the Walker Bulldog by Tamiya. I've never built it, but it got raves as a simple and cool-looking tank that is also easy to paint. Check it out. It's even in a Vietnam movie -- watch
Full Metal Jacket. They didn't fight with the Marines during Tet, AFAIK, but it's still great to see them.
Both kits are cheap and readily available. Heck, build them both!
Welcome to the world of big, dirty, very scary vehicles. Or modeling them anyway.