Unfortunately, if the actuator arm is broken, there is NO WAY to pop the glass open without removing the rear trim panel. And since you have to remove the trim panel without being able to open it, its very difficult and damage may result.
See, GM had the fore-thought to have a "plan B" should the solenoid fail. However, what they didn't realize, is that most "failures" were the result of broken actuator arms, and therefore the manual override is useless.
Here is the service procedure to remove the panel, however, you'll just have to skip step #1 and fight with it.
Good luck, and let me know if you need further assistance!
If the panel is carpeted (most are) you can peel the carpet back, cut a hole large enough to get in there. you will be able to see where the arm is broken and release it by hand.
Once you get it open and panel removed, you can flip the panel over, use adhesive (hot glue, epoxy, etc...) and some plastic from the craft store to re-install the cutout area. Once back together, use some spray adhesive to re-glue the carpet to the panel.
I have not done it that way, so I can't say if it would be easier. Alot of times if your careful, you can get the panels to flex enough to get it off, but I figured I would throw that out there since you asked.
Let me know if you need additional help!
thanks for the advise.....Being that there are screws involved peeling back probably would be the best way. I would be afraid that i would break the glass or do damage to the plastic. I cant believe that GM did not leave some type of access hole incase this happened.... oh well