I think they were still using the electric motor design in that era, I can't remember but if so there may be a metal panel under the cover above the floor of the step well that can be removed for access to the motor. You should be able to disconnect the linkage to return the step/cover to their step position and then diagnose if the motor is defective.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7