Dave,
if you still have the part that snapped off, I would recommend soldering it back together. Just carefully trim away about 1/8" - 1/4" of covering and then solder them together. Use just enough heat shrink over the splice to cover the wire and very slightly overlap the jacketing. Once you reinstall the receiver in the plane do a very thorough range check and make SURE that it checks out with the engine running. Also be sure that the solder joint is right, you dont want it coming apart on you. If you get the heat right and the solder wicks in you will be fine.

Even better than that would be to send the receiver back in to the mfg and let them fix it for you especially if it snapped right at the circuit board. Probably would not cost you but a few bucks and you would have a good as new receiver. I would not gamble with it, its your only link to the plane, if you dont get it right you are going to lose the airplane.