I couldn't tell you how, but I'd recommend researching here:
www.nicoclub.com/fsm
I'd also be concerned that it could be a gear other than the one on the motor, making the purchase of a motor an expensive and unnecessary step. It's also possible that the steering wheel column has something like the seat frame where the entire thing is an assembly that is meant to be replaced all at once and you can't easily replace an individual motor or gear.