R/C newbie looking for opinions-cheap radio!
I would not recommend AM for gasoline. I would instead suggest you look to purchase a reasonably priced FM system used here on the "classifieds" boards. There are literally a hundred different options out there, and its pretty tough to suggest a system for what you're doing because it doesn't fall into the 'normal' patterns.
MOST radio systems when purchased new come transmitter, receiver, at least one servo, maybe a speed control for motors, switch, charger if the radio has nicads, etc.
As far as where to buy, for your needs, quality used equipment here, IMO, is your best bet.