Cal 39 Mast Beam & Hull to Deck Joint Questions

I'm toying with the idea of buying a Cal. Maybe a 39 MK I, for reasons of economy vs. room mostly. Plus the dedicated sail lockers & pilot berths on the MK I, are choice features. But a 39 MK II or III, or a Cal 40 at the right price would more than do, knock on wood.

What I'm wondering is, is if any of the above, aside from the 40's (which definitely do), need to have the hull to deck joint glassed/re-glassed (especially the 39 MK I's). As well as how much of a pain is it to get out all of the old, dried out, original bedding/bonding compound from the joint first?
- Like, what tools does one use for said type of fun little venture when cleaning out the joint?
And then, of course, when resealing this joint, what did you use to do it? 3M 5200, some type of thickened epoxy, glass cloth/tape of some variety & epoxy, or... "Compound X"?

I mean, I'd love to glass/glue the joint together to re-seal things, including of course, using the original bolts. And then ideally, Heavily glass over the joint & bolts from the inside. All without making a major mess of the interior, etc.
And while I'm GOOD with glass, that one would be a Trick project, involving a lot of prep work & fore thought. Plus, likely a couple of sets of (experienced) helping hands.

Also, I haven't been onboard any of the listed boats in quite a while, but I understand that the Mast/Compression Post Support Beam can definitely be an issue (due to corrosion & it's location). A non-fun issue at that.
Like the video which I saw of a gent replacing the beam, main bulkhead, & compression post in his boat... after he literally took apart most of the interior structure of his boat to get to the beam's fiberglass casing. So that he could cut said casing open, in order to swap the old, rotting, galvanized beam, with a new stainless one.
Obviously that's something to be avoided. At least in my book.

So how does one check the condition of the beam in question without demolishing the interior + the structural bits of the boat? Barring drilling some strategically placed holes, & taking a peek at things with a steerable fiber optic camera.
- I'm sure it's "fun" finding one of those to borrow.

And I don't suppose that someone knows of anyone who simply made some strategic cuts into the fiberglass floor/glass beam, which houses the metal beam. And then replaced the tired old metal piece, with an appropriate composite structure?

Particularly as, after seeing how thin the metal is in the OEM piece. Plus the simplicity of it's design, I have trouble seeing it being tough to design something (even better than the original metal structure) out of composites, or a wood/composite structure.
AKA, a piece easy to bond in place, with similar mechanical properties to the hull, & where rot or corrosion will never rear it's ugly head again.

I mean on some BIG (racing, & of late, cruising) catamarans, the spar loading is handled by a composite beam not too much bigger than the mast really. And said beam also has to; span a HUGE width, & also withstand Gigantic racking loads from holding the two hulls together.
So... I don't figure my question's that far out there. Lil' help please ;-) .

Plus, I'm curious to know what mods owners may have made to these models of boats, & what if anything is/are their least favorite features about them?
Plus if anyone has any key, boat specific, inspection tips for 39's, 40's, & or other models, I'd surely appreciate them.

Thanks in Advance,
The man with "flexible" manners, AKA, UNCIVILIZED