I think the I32 deck is cored with Bruneel Plywood, an especially dense marine plywood. It's not balsa, and while the same technique probably would work. you might only have the FRP separating from the wood, which would be easier to deal with. It may not have water damage, just delamination. You'll have to get in to explore. If it is adjacent to the
hatch, it might be worth removing the
hatch completely, and going in through the exposed edges that way. And the reinstalling the
hatch, since presumably the water got in where the
hatch wasn't sealed down right.
Depending on where you want to take the boat, beware that the original Mark portlights are thin acrylic glazing--you can bash 'em out with an elbow or a hammer handle. If you're planning to go offshore, you might want to install something more robust.