speakers replacement on my '88 300ZX?

Hi-- I'm not even sure where to start as far as accessing or removing the
rear speakers on my ZX. I peeled off the ones on the doors, apparently just
basically glued on around the edges for the most part. But I'd hate to try
prying up the speaker-covers on the rear columns, mess up the vinyl trim and
discover that I actually had to access from underneath or something.

Anyone had any experience on this?

thanks,
Rob