Piece of cake, put one in the flathood myself. They are the ONLY way to go. The entire precedure involves cutting through the gooey seal.
1) park donor car facing south on the hottest of days. A few degrees make a huge difference in ease of removal.
2) remove interior trim along the top of the windshield and the side pieces.
3) use an awl or some tool to poke a piano wire, near the body, under the gasket. Stay away from the glass, easy to do. Alternatively, slide the blade of a putty knife or other tool through the seal and cut it that way.
4) with a person inside and one outside saw the upper seal and around both upper corners. You can now gently push the top of the window and with patience, fold it out slowly as the goo releases.
4) remove the window and look for a few rubber bumpers embedded in the residue at the bottom of the window.

The cleanup after extraction and after installation is most of this job.