No, there is no FCC licience to repair RC radios. There is nothing in the regs that require a licence, only Futaba and other demanding it is so. If you go back and reread the reg it says you cannot MODIFY the radio, it does not say you cannot service it. However it says NO ONE may modify the radio and that messing with the frequency so that it transmits on a non RC frequency is a modification. Therefore if you change the crystal you may be modifying the radio. Only someone with the proper frequency analyser and skill can do this and be sure he is not modifying the radio.