To change freq on futaba module series tx. All you have to do
is buy the module with the freq you want(Dont have to send in the
radio) to change freq.

You can change the crystal in the receivers to the same
freq of your radio with out sending tx or rx in. This will
allow you to run several models with on radio.

EX: Your radio is on channel 40. If all your receivers are high band
than just change the crystals to channel 40 in all your receivers.
Its ok to change the crystal in a receiver if you keep it in the
high or low range.