You remove the silencer by removing the heat shield. the heat shield has a hook on it that engages a hook on the pipe. It seems that there is a clamp around the pipe under there too.
It sounds like the C5 footpeg is different than the C5. But loosening the nuts at the head will let the pipe swivel around a bit, then you should be able to get to the nut.
If those lights like the tombstone had a ground wire, it would probably just be soldered to the outside of the light socket.
Bare