While your in there, maybe pull the signal light housing. The C5 has a problem with the DRL melting the top of the housing, making a hole directly over the bulb. Any splash of water, driving in the rain, washing the car will knock out the bulb.
I just did my C5, One 7 mm and one 10 mm bolt, and a spring to unhook.
Used some epoxy and some aluminum tape to repair the hole.