the wire cut method will work, but you may need to have some baby powder handy. If the seal is still sticky ( not likely, but maybe ) then you will have to liberally coat the wire with powder while you saw at it, or it will just re-seal itself. very frustrating.

The windshield shops have specialty razor knives, with high-leverage handles which reach in behind the glass and cut the seal.

Two things to keep in mind: if you plan to re-use the glass, and are considering doing it yourself to save money.. might wanna rethink that.

If you are tearing the car down that far anyway, and the glass is stock, I would recommend replacing the windshield anyway. Nothing as sweet as a perfect, new piece of glass to look out of at night.