[WDShaffer]

When using a knife to cut the seal, be very careful with the point of the knife, if it snags the edge of the glass it could crack.
If you have never removed a glued-in window:
1) use a fine braided wire like a guitar string or piano wire
2) always apply force parallel to the glass edge, as any small bending or pressure force on the edge will quickly break the window
3) use a gentle sawing motion with the force applied towards the metal frame
4) take your time if you want to save the glass.