One more thing... Say I spend a whole lotta green on a nice 75MHz FM system and my ghetto-engineered weed eater car bites the dust... Can the same electronics be swapped into an electric r/c car?
Absolutely. FM is preferable for ALL modeling these days, but AM is a less expensive option for more simplistic models. The radio equipment can be used in just about anything that is "main stream" RC (read not Radio Shak or other toy grade).
Take some time and surf
www.towerhobbies.com and
www.horizonhobby.com just as 2 examples of major distributors to show you what's out there in our hobby. You'll enjoy what you see, i hope, and it will help you better recognize what's available.