How do you change a brake light bulb on a 1997 Toyota Avalon?

Open the trunk. This will reveal two 10mm bolt heads on each side next to the light lenses. Remove the pertinent bolts. The entire assembly may now be detached from the body. There are two prongs on the outside edge of the assembly that pop out and into body mounts. Unscrew the bulb assembly desired and replace the bulb. Remount the assembly, insert the bolts and tighten. Done deal.

To change the highmount, open the trunk. Under the area of the highmount brake light there should be a couple clips that hold it in place, push them and the module should release from the rear deck. This bulb should twist out.