can anyone help me please.

a friend of mine has bought 2 Hobby Engine Leopard A25 tanks, at different times, for his 2 young boys. He has now discovered that both tanks are on the same radio frequency and the boys are distraught as they cannot commence battle against one another !
He has asked me to try and sort it out as I know a little about R/C ( I fly model aeroplanes ) Has anyone had the situation where they have had to change the frequency chrystals ? I have had a look inside both the Tx and the tank and found the chrystals which are soldered to the PCB`s. Now, I can de-solder them but there is little point without knowing what type of chrystal they are, I can easily get some Futaba or Hitec replacements on a different frequency but, will they work ?

any help gratefully received

thanks

Dave Cline