Dovetail saw
Well, you'll have a devil of a time coming close to matching the finish, but the first thing is to remove the molding top, bottom, and side. Then get a dovetail saw, which is a short (8" or so) offset fine tooth saw with a rigid piece along the back that is used for joinery work. If you use a block of wood as a guide it should be possible to make a good vertical cut down to the fiberglass on either side of the port where the wood is still sound. Then rip out the old wood and smooth the surface underneath.
The hard part will be coming up with a matching piece of teak plywood of the proper thickness to glue in place around the hatch. (If you do a search I think this topic has been covered, and folks have found that a cherry stain helps to match the original finish.) Once that is done, you will need to add at least one additional piece of molding forward of the port where the new and old wood meet to cover the joint. If you are lucky you might be able to carry the new wood far enough aft to the bulkhead to avoid a join between old and new wood there.
I had to do some work like this to replace my VHF radio in the Nav station, when the new radio was much smaller than the cut out opening for the original radio. I glassed the opening over with plywood from behind, cut out for the new radio opening, then covered the new raw edges with wide teak molding to hide the repair. The new teak molding I added didn't match the original, but it didn't look out of place.
And this has probably occurred to you, but I would get around to re-bedding ALL of the other hatches and ports before this happens again somewhere else.