Leaks and floor damage

[nskinner]

I have recently purchased my first AS, a '79 31' Sovereign. The exterior and frame are in great shape, and the axels, bearings etc have all been inspected and cleared or replaced at CanAM RV in London ON.
I have gutted all the fixtures and am at the point of inspecting / upgrading any plumbing, electrical and structural items that need it before starting the interior re-model.
As expected, there are a couple of areas of rot in the subfloor. One just fore of the access panel to the rear of the fridge and the other on the curb side front corner. There are 2 small splits in the outer shell in the area that are certainly contributing (not sure how these were caused), but I suspect that the seals on the access panels are also letting in some water.
I'm looking for any general thoughts on my plan: The areas of floor damage are actually quite small, about 1-2' wide and extending 4-6" in from the wall. Beyond that the floor is solid and dry. I have seen some posts on cutting out and replacing just the affected areas, which is what I would like to do. Any tips from anyone who has done this would be greatly appreciated.
I also would like to seal these fine splits without replacing the entire exterior panel if possible. They are small and I would think easily and neatly repairable with the right product, any thoughts?
Finally I want to replace all of the access panel seals. Does anyone know of the best place to get the right seals? Do I have to source originals from AS, or does anyone have suggestions for more easily accessible options?
Finally, are there any other "classic" areas to look for leaks on this model / vintage?
Thanks, I plan to post pictures of the progress as I go and I'm sure I will be spending a lot of time on this forum over the next year or two (or three or four...)

[68 TWind]

If the floor is not rotted all the way through you can do a good repair using epoxy resin and micro-ballon filler like that from West Systems. It is used extensively in the boat repair world. Lot of youtube stuff on how to do it. If the rot is really bad then you have no choice but to cut the old floor out. You need to make your cuts in the center of the frame rail and the outriggers. That will give you support for the patch. Getting the old wood out of the C-Channel can be a problem especially when you can't get to the underside. I tried several different ways to cut out old flooring but the best and easiest was a vibrating type saw (aka Multimaster, etc) that I bought from Harbor freight. The kerf is very narrow with these tools. You can angle it down and when the corner of the blade hits the steel of the outrigger you can just walk it down the line. You can also get right up to the wall. I would suggest getting a few extra blades.
On replacing the wood, plywood now days is not the same thickness as back in the day. I found that a couple of strips of roofing felt would bring the level of the patch to match the old floor. Use the self drilling flooring screws to secure the patch in the areas where you can't get under to put a nut on an elevator bolt.