I am currently doing the same job (amongst others). For those who think it can be re-veneered or covered with formica, I am now skeptical.
Mine is rippled. The bottom edges are rotten, dried out and delaminated. The original paneling is 1/4" and is glued to the cabin fiberglass. There is no core behind it -- so screws in the the fiberglass are out.
I removed the small trim fore and aft. I left the top trim that holds the headliner in place. I cut the paneling with an oscillating multitool following the contour of the top molding.
I removed the port lights and the deadlight panel. Cleaning up the chromed brass portlights and ordered the plexi/acrylic to make the deadlights. I managed to save the existing trim (shown in attachment) around the dead light. This was tricky since it is nailed into the original paneling edges with brass nails and glued with remnants of varnish. I restored the trim with wood glue and an 1 part acrylic wood hardener (minwax).
I ripped out the paneling. Process pictures attached. I had to work at a few spots but it was not hard to get it out. The fiberglass underneath is not neat and tidy. There were spots where the final layer of ply didn't come off, I decided not to care. I tried to remove some chunky bits with an electric planer. This worked well enough. I avoided getting into the fiberglass. So there is still some wood bits stuck there, I am pretty sure it does not matter. Note in the pictures. I could not tell if someone had laminated over the original or just painted it. It was a mess of delamination and dead wood.
To replace the paneling, I got 1/4" PVC foam board from eplastics. I bought it as 4 pieces of 14x48x.25 board. 4 pieces means 4 vertical joints, but less curves to deal with and much more manageable than a 14foot long wiggly wrangling exercise.
PVC takes paint well. Glues to anything, and cannot rot. I cut the top edge at 22degrees to match the contour my oscillating saw cut into the top of the old panel. I cut the aftermost piece to match the slope of the cabin back wall. So far it is a perfect fit. This is where I stopped yesterday.
This week I head back to continue this work.
I am replacing the headliner in the steaming berth, and the quarter berth. Both have alot of warp and funk in them. I cut the PVC coated masonite last night and trimmed the edges with vinyl tape. I don't think I will cover them with the foam and vinyl cloth initially. I want to see what it is like with a smooth flat overhead in those berths. I am insulating the SB overhead with glued in jigsaw mat (opencell foam) material, and insulating the QB ceiling with double bubble. Hoping echo from the flat hard ceiling is either not a problem or fun
I think the headliner has to be in place before the paneling is completed since the cut needs to be a continuous curve the full distance to look good. To do that I plan on tacking the rough cut panels into place with hot glue. And marking the cut line on the back of the paneling following the headliner and estimating in areas where I cannot get to mark.
I salvaged the old corner trim piece from the original. It has a lot of holes in it and and had to be glued in several areas where it had split. I may not reuse it however. I am thinking that a simpler white PVC molding will give it a lower profile, cleaner, more modern look. All installed with glue to the panel so I can still remove the headliner for wiring and leak issues.
Cost of this is good. I am only doing the starboard side for now, I am in it for $250 plus some labor. Nothing I have not done will up that by more than incidentals. I am supremely overconfident that this will work. Hilarity will, no doubt, ensue in the final stories.
