If it's just the gear itself that is worn and not the motor there's a possible cheap solution.
Depending on the gear it may be possible to flip the gear over so that you have new teeth in the area where they are needed.
Very often the gear doesn't turn 360 on a full run, therefore not all the teeth get used at all. Even if the gear does rotate a full turn, the very end run teeth may not be as worn as the ones at the top of the run.
It's an old trick taught to me by an RV repair guy for worn gears on the steps but it applies to all gear mechanisms.
Worth a look see!!