On my boat, that sketchy wood block was wrapped on the sides with a thin layer of fiberglass cloth. Not really bonded to the block, but formed around it.

If I was going to try to inspect it, I would look lift the floorboard and the little port in the floor pan that is just forward and to stbd of the mast step. Look in the hole at that fiberglass box around the mast support. If you can't get your head in, stick your digital camera in the hole and take a bunch of blind pictures, you'll be able to see quite a bit of detail.

What you are looking for is a collapse of this fiberglass layer. Mine had failed in the top inch or so, and was squeezing down over itself like the lid of a shoe box.

I think you could also easily drill a couple holes in that box and then probe the wood underneath. The wood removed by the drill should come out dry and a screwdriver should not easily pierce the wood.

Then you could squirt some epoxy back into the hole you made if things were looking good.

Also...

I think its likely that MOST if not all of our boats have this problem to some extent. There is no reason to take really drastic action if you are in a year-round sailing area and you can still get the rig tight.

However, the other stuff I did while the rig was out such as bonding the bulkhead, support beam etc. have made the boat seem much stiffer and more solid both on deck and inside. We have sailed the boat a couple of times now, once in big breeze and waves, and it feels better in a number of sort of intangible areas. I'm pretty happy now that I took the time to do it. At the time it was a major pain in the ass.

I'll also note that my total cost end to end on the process I documented in the other thread came in around $1,400 including new fasteners for pretty much everything and one new power tool.