A little searching will uncover a pictorial thread from about three years ago that is EXCELLENT. I can't remember the posters name, but he was from Oklahoma and had a moniker that was first name/last name or maybe first name/last initial. His first name started with a J. It will definitely be worth searching for.

Before buying a new motor, however, you should dig your way down to the blower motor and give it a spin to see if one of the fans has slipped on the shaft to a point of making contact with the housing.

Best of luck,