Hello,
It is good to see yet another coming over to the side of technology, the dark side.
If you just simply want on/off control of the motor, a relay would be an excellent idea. A relay is a simple device which allows a low power signal to switch a high power one. Imagine something like a washing machine. Say you want a guy who can't move to turn it on. So the feeble guy commands a strong servant to go turn on the washing machine. The strong servant is a relay. They tend to be on the cheap side.
If, however, you want variable control of the motor (you want to be able to control the speed of the motor from your controller), you need to choose something else. I would recommend a darlington pair NPN transistor (79 cents at radio shack last I checked). The wiring for a transistor circuit will not be difficult, but it is kind of difficult to transcribe onto Chiefdelphi. (If anybody knows a way I can post a circuit diagram, please PM me). The transistor must switch the high power inputs with a low power control signal. I would connect the control pin of the transmitter to an analog output of the controller, the collector to the motor, then to the negative terminal of the +12V supply, and the emitter to the positive terminal.