Hi,
the video
Repairing wipers at a Porsche 944 - YouTube
gives you a video tutorial how to repair the wipers of your Porsche 944. Dismouting the motor of the wipers is rather difficult for the late models.
The usual problem of the motor is rust caused by humidity entering in the motor housing. The video shows, how to bring the motor back to operation.
Enjoy it,
Jürgen