You should be able to pry rubber back from inside the cabin whilst maintaining pressure on the glass and start working your way around it until it pops out. I generally spray around the rubber with some soapy water just to make the rubber slip away a bit easier.
When putting it back in get a piece of nylon cord and tie it into a loop in the rubber locating channel. Get someone to help you...they can sit in the ute tray and press the glass (with the rubber sitting around the glass) up to the hole in the cabin. Pry some of the rubber lip over the opening and then you should be able to get hold of the cord that is looped in the rubber channel and start pulling it around the edge....it should pull back the inner lip of the rubber and by the time you've pulled the looped cord out the window should be reseated just like it was before you started.
Hope all that make sense
