Mk I, II, III, IV or V?
I'm not an expert on all things C&C, but they seem to have used a slotted aluminum toe rail on nearly all of their boats. The lifeline stanchions are attached to the toe rail.
If the deck has been stressed in these areas, I can't imagine that it would be very difficult to do some local re-coring of the deck to fix this. Tedious, irritating, yes. It's kind of hard to judge how bad this is without photos.
C&C's are a higher quality build, a step up from my Pearson. Most of them sail well. I would look for bigger deal-breakers like a dead engine, failing standing rigging, or major deck delamination. I wouldn't let a few deck cracks scare me away if the boat was healthy in other respects.