I own a 1995 S 420. I noticed the driver's side windshield wiper, the longer of the two wipers, is not getting the coverage it had. It seems as if the arm is not extending out as far as it sweeps the window. I wonder if this is the dreaded wiper transmission problem that is costly and time consuming to repair?

I often wonder how many times chuckG will start this thread

Your wiper transmission has probably failed, it has a feature that extends and retracts the blade as to wipe the top left corner.
It's a $1400 part
It's a fairly common problem and many have found it to be a gear that breaks inside the tranmission. A few have had a new gear made and put it in with success. I've tried but couldn't get the transmission apart, i drive with it broken now. No big deal.