I don't know if this is a problem on the Mercedes as much, but on my VW the windshield is glued in and the level it sits at is very important. About 2 years ago I had a terrible time getting a glass shop to install a new windshield properly, they couldn't seem to get all the old glue out and the glass seated at the correct level... it sat too far out and made a tremendous wind racket. That looser shop cut my headliner (which is now falling down) and scratched the paint in a couple places... and also tried to tell me glass with the tint strip at the top wasn't available anymore (nevermind they are still selling that model new with said glass), then the guy claimed to be an expert in VWs because he once owned a 78 Rabbit and said the wind noise was normal
They ended up installing 3 different windshields before I said enough was enough.
When my benz needs a new piece of glass I won't be taking it to that shop...
-J