I can't find a detailed picture of the front of a C but it seems close enough to a B. There are 3 radial screws that hold a trim ring around the lens - back them out and the ring falls away. Inside are 3 cross-slot screws that need to be only loosened to free the steel stop ring (scribe everything before this if you need) and allow the lens to unscrew.

The rest is ordinary, and somewhat hazy. The nameplate comes off the lens with a rubber only - no locking screws but a dented ring will raise hell.

Like I said, a hazy memory and a different camera, but there aren't any unmanageable surprises.