From the looks of it i would take a pass on this boat.
Not to discount what the surveyer said but he's not the one who will be doing the work and its easier said than done.
My guess is that these repairs will outweigh the value of the boat, even if the boat and your labour is free.
locally I have seen these boats for sale between the $3500-10000 mark, most with simple cosmetic issues and/or old running gear.
I bought a previous boat, a mirage 24 (also a c&c design) 8 years ago for 5k.it had a fairly new 10hp honda,new harken furling,fairly new sails and a solid hull and deck with no moisture.
when i was at a freinds marina last fall i saw this boat Pat Sturgeon Yachts Search Details
, a solid boat that just needs a cleaning.
you will likely spend the asking price in materials before the said c&c hits the water.
For that area to have dimples that severe its pretty much guaranteed that there is moisture in the core.
Also, remember the keel is bolted thru the bottom of the bilge, if there is moisture there and its not repaired it will get worse and make a safety issue as this is a major structural area.
The problems will get worse if you dont cut out the damaged areas and remove the wet core as the moisture that is there will spread and eventually cause delamination to any repair you perform.
Once the core is wet it will only get worse, you cannot isolate it safely.
I personally wouldnt get involved but if you must, you have to do it right or its a waste of effort.
If i was tackling this repair i would work from the inside and cut the first layer of glass until all damaged core is exposed.
once the core is removed it will make the outer layer of glass easier to work with, then you can build on the outer layer of glass to fair it, lay down some new core and build another layer of glass on the inside.
On this boat the bulkheads are bonded to the hull.
If you "patch" the bulkheads this will take away from the structural integrity of the boat and eventually the repair will fail.
You would have to cut out the headliner around the area for access and then remove everything attached to the bulkhead.you can then make a duplicate of the bulkhead and bond it to the hull and then glass your headliner back in and reinstall what was removed.
What did the surveyor have to say about the deck, mast step and cockpit floor?
Just talking about this makes me itchy.