2000 Grand Caravan wiper problem

It appears the gear is stripped in the wiper gearbox. Can just the gears be replaced or does the whole gearbox and motor need to be replaced? Any advice would be appreciated. Thanks.

To clarify, the wipers move together to the up position, then stop and there is a load buzzing noise. If you turn off the wipers they stay there and the buzzung stops. With the wipers on, if you push on the passenger side wiper, you can get it to engage and both arms will go to the down position. They always stop at the same place in the up position. And you can't push on the drivers side arm to get it to engage.

Is this something that is easily replaced or do I need to seek professional help?

No experience with it but, may be a bad park switch in the motor asssembly. Not positive but, I think you have to change the motor assembly for that anyway, unless you are they type who can go where few have gone before.

http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528003c621 Click the pics to blow them up.

You can get a 2 jaw puller for $15 if needed.