I'm going to go slightly out on a limb.
I've installed about 5 window glasses. One was a windshield. One was back glass, and I've done the pantera side glasses a couple times.
To install the glass (I know you said remove), you take a piece of rope or wire. The last time I used weed-eater nylon string. You put the gasket on the glass, then you insert the rope into the lip of the gasket. You lay the glass on the car with the ends of the rope on the inside of the car. Then you pull the rope into the car. As you pull the rope, it pulls the lip of the gasket over the metal lip of the window frame. Tada!!
To remove, I'd think you could do something similar. If you could get a small rope pushed though the gap between the gasket and the metal lip, you could pull it all the way around the frame, gradually "unseating" the gasket.
Make sure you use a small rope, but not something that will cut the gasket. That is, safety wire won't work. Soapy water may help.