Bruce, I believe TX crystals that plug-in are changable by the unlicensed consumer. I have never seen any cautions about changing crystals in RC equipment other than cautions about ensuring that the TX is intended for Upper or lower band for the 72 Mhz aircraft range or the entire 75Mhz surface vehicle range.
I agree that if you start unsoldering parts in a TX you need to be licensed AND know what you are doing.
If I am wrong then the entire industry is in violation.