If you're planning to replace the speakers, don't worry too much about messing up the speaker covers. They're trash too. Just use whatever tool you need to yank them off. The screws that secure the speaker will be visible once the covers are removed. You can remove one of those old speakers and take it with you when you go to shop for new speakers. That will make it easy to find new speakers that are the right size. Don't forget to consider the depth of the new speakers if they're installed in a tight space. Installation of the new speakers should be pretty easy.
When we took delivery of our new AS in 2001, it didn't take me long to discover that it came directly from the factory missing one of the four speakers. Rather than going back to the dealer and getting a replacement, I took the opportunity to upgrade to new Infinity speakers. I still have not regretted that decision.