Not sure if your car is different than my '96, but if you have the Mach system, then you have to remove the speaker grill, then the speaker, and the three nuts should be right there and accessable. I didn't have the Mach system, so I just have a plate that pops off and the nuts are right behind it..
If you find a way to pop the glass out without breaking it, please post it here. I don't think the glass piece itself is considered a replacement part, although I've been wrong thousands of times before.
That might be a good question for Randy Stinchcomb.