if you want to change channels on a TX and RX you will need to send it in to be retuned to that channel you can not just change crystals.(at least without taking a chance of trouble like losing control of your plane) altho i know people do it and say it works just fine but all it takes is just once and someone gets hurt or WORSE .check out futabas website in there FAQ sections it tells all about radios do`s and dont`s hope this helps.

http://www.futaba-rc.com/faq/index.html