I can give advice on the headliner, and that is "let a professional in the upholstery business do it". Sheesh, for all the labor you're going to pay for, look what you get? A finished job that looks professional, using professional tools and snaps and fasteners. Surely there is a marine upholstery guy in your neighborhood who does this for a business, that's who I would call. You can get the pinhole headliner that is exactly what CC usee, or so close as to not be an issue. I had mine done many years ago, still looks bran new.
Regarding the side panels, I don't know how a 31 is fixed, and it may well be someone fixed yours down with 3M-5200. If they're damaged coming off, you can still use them as a pattern for new panels, they make a nice mahogany ribbon sliced 3/8" marine plywood that works great.
Here's a couple views of my helm station, all the wood on the bulkhead side, around helm, door to cabin, etc., is original. The side panels are new ribbon sliced phillippine or african mahogany plywood stained to match. My original panels were painted white, not sure if that's the way the boat arrived at the dealership in 1966 or whether a previous owner painted them white. In any case the wood along the sides is a major upgrade. I finished them in the shop laid down flat, no runs that way, varnish goes down nice and flat, used a foam roller and tipped it with a brush when needed. Don't lay it down with too heavy a film, it will soften the underlayer and cause a wrinkle.
Regards,
Paul