Illegal is nothing more then A sick bird!! I'm sure the person at the hobby shop thought you meant the module because it's often called the radio crystal depending on who is speaking. Common error. We also found out early that the Hitec Spectra fit right into the Futaba radios so you then had it all, sort of. Then the AMA came out with the statement about that sick bird thing again when using the Dialacrash in any radio except the Hitec. Changing your module to change your channel is nothing new, done all the time.
Jester brought up A great point though, if you are starting from scratch then you may want to give the 2.4 switch A thought. In my case I have so many RXs and planes I'm priced out of the change. If I was just starting out then I would switch over right now.