A replacement gear kit for this motor is available at Autozone. (Part No. 42-91) This will most likely have to be ordered. You can do that online or at the store.
See this link:
http://www.autozone.com/R,APP855080/vehicleId,1764401/initialAction,partProductDetail/store,1308/partType,00696/shopping/partProductDetail.htm Current Link For Gear As Of 03/12/09The kit is $15.99 plus shipping to your door.
The replacement kit is for all Taurus and Lincoln window motors (same used on Kwikee).
If the motor works but the step is bumping or sticking against the stop, try this option first.
Just remove the motor gear cover lock pin (c shaped) and the gear case cover screw. Pull out the plastic gear set, replace with new and reassemble.
Edit to make link clickable. Mel