I, too, have a question on replacing the backglass.
I removed my Williams 4-player backglass probably a year ago. (It just lifted up.) I cannot fit it back in, though. The lift bar has nibs that prevent the glass from seating all the way into the channel. Thus, when the glass is inserted into the top slot, the lift bar extends past the bottom slot and cannot be raised high enough. I tried to hammer the bar to seat it but this didn't work.
Any suggestions?
BackGlass Botton Lift (resized).jpg