fwiw, I keep spare gears for all my servos in the shop. gear replacement is really quick and easy, and gears are usually $2-$3 for your basic nylon geared standard servo, depending on the brand.

For some odd reason Tower charges an arm and a leg for gears, but other hobby shops, such as Servo City, charge a lot less for the same gears. I don't know if SC has Futaba gears, I mostly get Hitec from them. So shop around if the price seems high.

I also agree that it's worth doing at least once on a cheap servo now, rather than waiting to learn how on a much more expensive servo.