My 90 300E 2.6 is essentially the same car. When I did the blower motor, there was no real danger of stressing or cracking the windshield. I didn't even use tools to take the trim pieces off, they just pop out.

It's possible that they dropped a tool near the edge. It seems like a very suspicious coincidence, however it would be tough to prove anything in this case. Sorry, that's a bummer.

On another note, I'm surprised that they charged you the labor for the R&R on the blower when it was a misdiagnosis. The blower motor can be checked by applying voltage without any disassembly. Was it their misdiagnosis, or did you specificaly ask them to change it based on your own diagnosis?

__________________
D.H.

04 ML500
02 E430

Experience is something you don't get until just after you need it.