Although not familiar with motorhomes I've worked on many automotive power windows, often the switch itself can go bad, do all the other windows work from the master switch ? If not then the switch or power feed is a likely suspect. If all other windows work, still suspect the switch as the drivers window and switch are generally most often used. You can find a wiring diagram and attempt to bypass the switch for the final diagnosis, just short the correct wires on the backside of the switch and see if the motor operates, if the motor does work then the switch is probably bad and should be replaced or if you're really broke/bold you can carefully dis-assemble the switch and clean the contacts of the switch just beware springs and copper tabs will probably spit out and require much work to get all back in place. The true way to confirm a bad motor would be to apply power to the motor from an independent 12v
source like a battery and confirm the motor is shot, polarity is not important, it just affects the direction the motor turns. Last, generally you should be able to access the motor after removing the interior door panel although I have run into some saturns that require removal of the OUTER door skin to access the window mechanisms.