The user must insure that when they use their transmitter, it complies with the technical specifications for the R/C Service. If you cannot do this, you must have someone do it for you.
To change a transmitter crystal, you first swap out the old crystal for the new one. You then turn on the transmitter, extend its antenna, and put it in the location required to use your spectrum analyzer. The spectrum analyzer will have a calibrated antenna. You check the center frequency, and adjust it as necessary. You check the power output, and adjust as necessary. You check the FM deviation, and adjust as necessary. You check the bandwidth and adjust as necessary. Finally, you check the analyzer's display at a wider bandwidth to double-check the skirts of the output spectrum.
If you have the proper equipment and training to do this, you are qualified to perform a frequency change.
The applicable FCC regulations can be found at:
http://www.access.gpo.gov/nara/cfr/w...7cfr95_03.html
The technical requirements for R/C are in Part 95, Subpart E, which starts at 95.601. If you don't understand these requirements, and/or don't have the equipment to insure your transmitter complies with them, then you are not considered to be qualified to change the frequency of your transmitter.
An FCC General Radiotelephone Operator License is no longer required to work on R/C transmitters, but most RF service shops have at least one person who holds that license. Even so, without the proper test equipment, even a trained/certified individual cannot assure that a transmitter complies with its technical requirements. How can the untrained layman?