Sounds like you are still trying to sleuth out which Jayco base model this Conway was built on. If you take a look at
1986 Jayco Price, 1986 Jayco Values & 1986 Jayco Specs | NADAguides you will see a fairly comprehensive list of the Jayco Camping Trailer (popup) models for that year. Further narrow it down by the length of your trailer (I am guessing they are listing total length, not box length) - from the picture it looks to be about 14' so would leave you with 6 possibles. Now do a quick google search for the remaining possible matches and look at the pictures - this will usually give you a floorplan and interior images that you can match against your own; use some caution, and click through the links to confirm as there will be a lot of pictures of near matches as well. By process of elimination you'll probably come up with the right one. From the half I can see, the configuration of the dinette, kitchen cabinet and door side cabinet looks like a Jayco 1007, but that model wasn't in the lineup yet in '86.
As far as the wall goes, I would think it should be doable without completely removing the walls but have I never done that with a trailer (I have done it with a garden shed, similar but not the same). I would want to be sure to cut at a cross member so my patch had a good support on 1 edge at least. If you cut away any attachments of the wall to the floor in the patch area, and a little beyond, and then drive a couple of wedges under the wall on the good side of the cut, you should be able to lift the wall just enough to slide the old piece out, and slide a new Dutchman in.
ETA: I'd probably use something more "subtle" than my reciprocating saw to cut away the wall attachments so as not to damage the exterior surface, probably my multi-tool would do
https://www.ryobitools.com/power-too...ool-attachment
Certainly worth a try now that you are so far into the project!
Good luck with this!