Neal,
You are probably right about the cause of the leak since there really isn't much else that penetrates the deck at that location. Once you remove that plywood panel, you can look at the back side of the panel and I'm sure you'll see drip marks that line up to the bolt location. This is a two person job, one on top with a screw driver and one below with a socket wrench. When I re-bedded mine, I drilled through with a larger bit, filled the holes with an epoxy putty, let dry, mark and drilled new bolt holes trying to stay in the middle of the epoxy plug. Use a countersink bit once the new holes are drilled to indent them a bit to allow a good seal with the caulk. The deck coring at this location is plywood for strength, but if it has been leaking for a long time, you'll need to let it dry for awhile once you remove the track/bolts. Tartan usually seperates the plywood core from the balsa core with resin, so even if the plywood is saturated, I doubt it migrated to the balsa, Ideally.....
Removal of the outboard galley cabinet was a bitch. It was really a tight fit, but it does come out as a single unit. If I remember correctly, a Sawzall was involved

Once you remove the trim pieces, see if you have enough clearance, I did not and used the saw to cut about 3/8" along one side which allowed me to pull it out. Mine was probably a pain because I tiled my countertop which reduced the verticle clearance by 1/4" which might have affected my ability to manuever the cabinet, but it is still a tight fit.
Once you get this cabinet out, buy a few cans of spray foam insulation and squirt it in the void that is outboard of the icebox. It is amazing that Tartan did not insulate this space since it heats up a lot with the solar heat gain on the hull. You'll notice a difference on the refigerator/icebox .
Have fun,
Tom