From time to time I have seen that some magical annoiting must proceed legality to change a crystal. Turns out not only can you change a crystal, but if you want to change every componet in your R/C transmitter - Your legal,
The following is from the FCC website as to what services are exempted from requiring a commercial license to maintain a transmitter:
You do NOT need a commercial radio operator license to operate, repair, or maintain any of the following types of stations:
Two-way land mobile radio equipment, such as that used by police and fire departments, taxicabs and truckers, businesses and industries, ambulances and rescue squads, local, state, and federal government agencies.
******************************************Personal radio equipment used in the Citizens Band, Radio Control, and General Mobile radio services.
***********Emphisis added ******************** Auxiliary broadcast stations, such as remote pickup stations.Domestic public fixed and mobile radio systems, such as mobile telephone systems, cellular systems, rural radio systems, point-to-point microwave systems, multipoint distribution systems, etc.
Stations that operate in the Cable Television Relay Service.
Satellite stations, both uplink and downlink of all types.