Replacing Brake/Stop Light Bulbs

I have a 1997 Camry. Recently, the stop lights warning light (far left warning light) came on the dash. All the stop lights work in the back (including the one on the center console) and I know it may be a problem with the wiring harness, but I first want to check the bulbs. I've tried to follow the instructions in the manual for pulling the bulbs out and opened up the plastic covering in the trunk. The white assembly holding the bulb doesn't seem like it will move. What am I doing wrong? How do I get to the bulb to check it out. I'm trying to make sure that I don't break anything. Thanks in advance for all your help.

Did you figure out the bulb replacement? I've got a '96, and after pulling the trunk lining and the wire seal, I didn't see a way to get at the bulb without removing the entire brake cover. There's got to be an easier way!