Need help repairing Bachmann HO 2-8-0 steamer.

Could be. You may need to take the shell off and make sure that the drivetrain is all in tact. When you say you can hear the motor "run" I am assuming you mean it is actually turning and not just buzzing. Otherwise, I might also suggest that the gears may only need lubrication, or that there could be an issue with the motor after all.
If it is the gears or a drivetrain part, I would assume you could order those from Bachmann somehow. I have never tried to repair one of their locos so I am not much help beyond what the problem could be. :)
* SLMR 2.1a * All animals are equal, some more than others.