Welcome to the family and congrats.
As stated the deck compression may be the wooden block in the bilge which supports the compression post. Catalina Direct used to sell these (white oak?) but not sure if they do anymore. Some people build their own post out of stacks of fiberglass resin sealed wood, or all fiberglass (no dampening with fiberglass). Requires jacking the cabin overhead up to relieve pressure while dong (best with mast off if you can...)
Compression could also be due to rotted plywood coring under the mast in the deck.
Attached is the Catalina drawing for the keel bolt wood repair. This (obviously) has to be performed with the boat out of the water and the keel supported
Some to-do's with a Catalina 30...
-Remove the upper shroud chain plates and inspect or replace them (cracks). Catalina Direct sells replacements. They obtain them from Garhauer Marine (excellent source of blocks etc.)
-The side windows are probably leaking (rain water). Only way to fix is to remove and re-bond (3M 4000 / 4200) to the deckhouse. Fix any plywood rot before. Catalina Direct sells a kit to replace the gaskets in the glass.
-Check the thru hulls . Replacing the 40 year old originals (resined in-place pipes) is probably a good idea.
-Remove and re-install the lifeline stanchions. they become loose and let rain water ingress over time. Replacement stanchions can be found online or at Catalina Direct. If you need to replace the life lines they also sell a kit or you can by the parts yourself. (C.S. Johnson -
C. Sherman Johnson Co., Inc.) . Some marine distrbutors sell them as well. I was quoted $3K to replace the lifelines only by a rigger. I put al lnew stanchions and lifelines myself for one third of this (in 2020...prices are now higher..)
cheers