Your really sure the stepper motor is bad. There is not a whole lot that can go wrong with a stepper motor. In most cases the electronics that drives a stepper motor will go bad by a ratio of 10 to1.
Is the stepper motor actually sold all by itself or is the "package" of the stepper & driver electronics sold as a "motor" when it actually is not just a motor. I hate to see you finally find a motor only to discover it does not fix your problem.