Yes, it can run on Win7 x64.
Uh... you have $6.50... isn't it $7.49?
If you've played the classic Command & Conquer games, don't bother. Red Alert 3's different, shallow, annoyingly "wacky", and has retarded shit that will piss you off.
If you haven't played them before, then give it a try, because it probably won't grate on your nerves as much, or at all.
I'd consider C&C3: Kane's Wrath to be the better game though, out of the two. Or three. Because Kane's Wrath is an expansion. But you can't buy both Tiberium Wars and the Kane's Wrath expansion, because that's double the price. But... $12.50 combined. I dunno lol.