There's supposed to be a length of nichrome wire that runs through the windshield seal. Attach it to a battery and it melts the seal, window comes off. That said, when I had the windshield done on my 190D, I had a glass place come out and do it in the parking lot at work. They weren't able to get the old windshield off in one piece, not that I cared. It would be a horrible job without two helpers and their special tools. Horrible. it was the best $200 I ever spent. This was the place I used:
http://www.windshieldstogo.com/
They coordinate with local installers all over the country. Their negotiated price is lower than if you were dealing directly with the installer.