i saw a "myth busters" episode on discovery channel where they made a 1:1 car radio controlled, they used a 9 channel stick radio. a few big servo's, a motor off a wheelchair to turn the wheel, a lot of relays and some pretty ingenious ideas.
it is very possible, but you need to plan it all out before starting (what car are you planning to do this to)
Good luck brett
(i just noticed were all NZ'ers in this thread hehe)