This comes up every six months or so. As Ken pointed out, it is illegal to swap out your TX crystal yourself. This has to be done by a qualified service organization (Radio South, or the radio manufacturer) and then tested to insure that the TX is tuned to the center frequency. If you swap it out yourself, you can almost guarantee that you will be operating over someone else on an adjacent frequency and will be the cause of a crash.. or worse.

If you want to avoid this, either leave it alone or go to Spread Spectrum like a DX7/DX9?Airtronics RDS8000, FASST and forget about it.