That gyro isn't going any where and Ricks http://www.ronlund.com has it for less (you have to email them for a quote but it will be 120 plus about 3 bucks priority mail shipping)

You really can't turn it "off" from the transmitter, you can switch it back and forth between AVCS (heading hold mode) and Rate mode by setting the end points on the gear channel (or any channel w/ a toggle switch) the end point being the gain percentage for that mode, in a plane I would be careful using heading hold mode as the results won't be quite what you expect. If you have a fancy radio with a gyro menu like the 9c you can set both sides of the switch to rate mode and a very low gain on one end which will in effect turn it off.

Also no worries mail ordering from Ricks they are the class of the business as far as heli's are concerned.