Futaba 3GR owners (40mhz)

[Nightshade]

Right, I feel completely stupid asking this, but having spent over 2 hours playing with my new (to me) 3gr, I cannot for the life of me how to switch frequencies. Can anyone help?
It came with no manual, and the one from the futaba website is for the 2.4gig version, hence no section on changing frequencies. I'm not even sure which channel it's currently using, but I'd like to be prepared for tomorrow so I can change if needed. Also race control will want to know what I'm using too right?

Google has been useless...