Ceiling Repair Question

Hey everyone, new here, my wife and I are still in our first popup, which we got 3 years ago. The thing has been nickle-and-diming us since we got it, so I'm doing some final repairs before selling it this spring/summer (hopefully). It's a 2000 Coleman Fairview, big dual-king monster with a center slide.
Shortly after we got it, it developed a leak in the center seam. This was evidenced by water draining into the rear light fixture, filling up with water, and then dribbling onto the interior of the roof canvas while folded up. Spared damage to the rest of the pop-up, but left a nasty stain on the canvas roof. Anyway, we got it re-sealed, and the leak is gone. What I have left besides the big brown ugly stain, is the ceiling panel at the rear which is rippled from the water. I've seen a number of threads on here on to ascertain that the ceiling is probably vinyl covered luan. My question is this: Would the vinyl shrink up under heat (from a heat gun) and tighten back up? If so, it might discolor, but that's nothing a paint job couldn't fix. If not, is there any other solution to make this repair without having to do a complete disassembly of the ceiling/roof?

Bonus question, any ideas for cleaning that bit ugly stain out of the ceiling canvas?

 

I expressed concern to the RV shop that fixed the leak in the roof, they seemed to think that the mold risk was low, they tried to dry it externally and I left it popped up for a long time to let it air out, even using a dehumidifier in there. This was 2 years ago.

I did see the cleaning instructions of the manual, I was more curious if there was anything else, as this is rust stained water stain, and I know rust isn’t an easy thing to clean off.

 

No, I get it, i know how evaporation works, the leak didn't happen while it was collapsed or in storage while sitting around, it became apparent while it was up, had to collapse it to get home with it, so it really wasn't sitting for months, but hours cumulatively between travel and drying out both in our place and at the indoor shop. I'm going to try and get an inspection cam up into the cavity to have a look. I have neither the money nor the time to disassemble the roof. Assuming the wood isn't rotten and moldy, I'm really just asking how I can smooth out that ceiling without disassembly, whether the vinyl would contract when heated or things like that.