Unfortunately, the manufacturers made it to easy to simply go ahead and change the crystals out. The bad part of this is the liability that is assumed once you change the TX crystal. If it is off frequency (It is not simply a place holder, the actual transmit frequency is changed and must be centered on that frequency not on the left or right of that center frequency) it will intefere with the adjacent frequency. It also could 'spatter' over other bands if it is not done correctly.

When they (radio shops like the manufacturer or Radio South for instance) swap out the TX crystal, they will check the output with a spectrum analyzer and see where the center frequency is and adjust it accordingly (if needed). Most systems use a phase lock loop system that digitally locks the frequency on center. What can be a problem is if you have a crystal that is problematic, and you will never know it until it causes problems, it could spill over to another channel and cause that channel to be corrupt. This will cause someone on that channel to have some serious problems.

So, you cannot just swap transmitter crystals out. Receiver crystals, on the other hand, do not transmit anything (for all practical purposes). So, if it does not work you will know it right away, or if it is not exactly right, your range check will fail. Easy to tell. Not so with the transmitter.