Replacing the 3rd brake light on a C5 is fairly easy. The first thing you realize is that you can not access the brake light from inside the trunk. The easiest way to do it is to remove one of the inside tail lights. Just remove the two screws holding the tailight in place and the assembly will pop out. From there you can reach your arm inside the bumper assembly and get to the 3rd brake light mechanism. Two nuts hold the assembly in place and are fairly easy to remove. You also have to remember to unplug the light from the main electrical cord which is located close by the assembly. After completing this process yourself you will feel like Mr. Goodwrench.
