Access to Wiper Motor '91 SL

I would like some advice in reaching to the wiper motor and linkage on my 1991 300 SL. I've had the linkage lubricated several times by MB shops but
this has not prevented the wiper from stopping. When I need the wiper while driving in the rain, it will run from 5 to 10 minutes and then stop. It may start again on it's own or I can change the speed and to make it run again. But this trick is only temporary before the wiper stops again.
The repair shops can not duplicate the problem, so they lub. the linkage and move to the next job.
It has been suggested: replace motor, linkage, switch, etc to solve the problem once and for all. This seems to be overkill. I would like to try to find the root cause for the problem myself and save a few dollars while learning.
Any suggestion would be appreciated on how and what is needed to gain access. Or a web site showing how to remove the arm, hub, etc to reach motor, linkage, etc.
Thanks John
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