Superb advice from Silver Fox!
I wish I had read the tip first on releasing the cover to the slides; I have just managed to shatter the large cover on my C220 by prying a bit too energetically in cold weather. I had lubricated the twin-shafts about 12 months ago, with waterproof grease, which has turned out to be too thick in winter, and tends to stick sometimes.

A bit of encouragement for the faint-hearted, last year the nut holding the whole arm to the wiper drive came loose, so that the arm was not moving at all. You can imagine my distress at the thought of what this was going to cost me!! What's worse, I was due to travel 150 miles to an unmissable meeting the following morning, it was now 8:30 PM and getting dark, with heavy rain due overnight.

Desperate situation requiring urgent action!

I removed the whole wiper mechanism, just tightened the nut enough to hold the arm in place, then offered up the whole assembly, and corrected the position of the arm on the windscreen/windshield, then very carefully removed the whole assembly again and fully tightened the arm-nut in the right place. It was then straight forward to replace the whole lot back in.

This all took me only 1 hour and 45 minutes, with the car on the driveway, (garage occupied with rebuild project) and my long suffering wife passing tools and holding an inspection lamp. The hardest bit was removing the leaf shield without breaking any fiddly little plastic trim clips.

The point of the above, is to emphasize the comments elsewhere in this thread, that it is not difficult for a (supposedly) competent DIY'er to avoid big charges for wiper mechanism repairs.

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W202-C220D ( UK ) 310K miles