Got a few things done over the weekend at the shop. It never seems like enough, but I'll take what I can get.
So, I've been munging on this delamination fix over and over again and I finally settled on rebuilding the inside with luan (1/8" plywood) and wallpaper. On the outside, I settled on the 3M panel bond. I decided this after poking around again in the area where the delamination happened, which is under the washer and dryer. There's an access panel below that I pulled off that exposes the bottom of the washer cabinet and one of the heat exchangers for the aquahot (furnace). I poked the wall with a screwdriver and there doesn't appear to be any rot other than what I knew about, which is in the bottom of the bathroom, linked to that wall, which I already knew about. Can't find anything else. So, panel bond it is.
Other indicators of water intrusion are the spray patterns on the side of the coach from the trip back. The entire passenger side is covered in spray. Also, looking up at the bottom of the sidewall with the basement doors open, I can see the luan that the sidewall is bonded to. The bottom edge has signs of water/rot all along it. I suspect this problem is a combination of a bunch of things. Age, water from driving, and water damage from whatever leak happened. I'll be doing a full reseal as part of this fix (top and bottom).
So, I pulled the rear fender, which required removal of the rear door covering the battery. The rear fender was found to be missing one fastener on the side (rear). It also had spray foam along the inside (front) and some sort of black caulking along the front edge. I'll be replacing those as I put it back together. There are also several areas under the coach that have a piece of thin wall tubing, around.25 diameter that is flat on both ends and they screw into the fenders. This keeps the bottom free edge of the fender from flapping around in the wind. They also like to go missing from time to time. The front one is on, but there's not one on the rear half of the fender. I'll source something for that as well. I've seen folks use all sorts of stuff for those, but I'll try to find some tubing close to what the factory installed.
Moving inside, in the toilet room, I needed to remove a few more bits on the outside wall, which I did, in preparation for the new luan and wallpaper. Did you all know that wallpaper isn't really sold in stores any more??? Home Depot, Lowes, Menards, etc don't carry it in stock. You can get it on Amazon and places like that, mostly in the form of peel and stick. My BIL has a '17 Thor with peel and stick, and you can guess what's happening to him. It's peeling in all the corners. So, not what I'd rather use. I'd rather use a pasted wallpaper, which I feel will stand the heat cycle better. And wouldn't you know it, the paste type is about 4X the cost of peel and stick. Dumb all around. What I did find out is that the coach manufacturers glue the vinyl "wallpaper" to the luan and then use those panels to build out the coach walls. Some use vacuum to seal it all together, though I don't think Monaco did that in 2007. In any case, the course of action from this point is to glue 1/8 plywood sheets to the walls that I've removed, smooth out the joints, and then wallpaper with real wallpaper and paste. Unfortunately, I need to wallpaper over the small areas that I'm not removing and I don't like that. I dislike wallpaper so much that I swore after removing it from homes so many times that I lost count. Heck, It's one of those house projects I never learned how to do because I dislike it so much. That and carpet. Anyhow, I'll be putting it in the coach and learning along the way how to do it.
The other thing that I got accomplished was to swap out the starter on the Excursion. I generally buy auto parts at Autozone. I know, I know. However, a lot of their parts carry lifetime warranties and they have locations about everywhere. If I'm ever traveling, and something breaks, many times I can just pull it off and go get a new one. The X has been starting a little slow lately (turning over slow) and finally the started just didn't have the oomph to turn over the 12V. So, I pulled it off and took it in to go warranty it. They hooked it up to their tester and it spun. Said it was fine. I told them I'd check other potential problems and get back to them. Next day, I went back and the same person was there. After some conversation, she gave me the new started and sent me on my way. Put it on, and she spins fast again. Bottom line, the starter was just weak enough and on it's way out to not spin the motor over. And now for some pictures...

Needed to remove the dock light and clearance light. I ended up cutting the clearance light wiring as there's about 3' of extra wire behind the fender.

Screws holding the fender on. There are 3 at each end and one at the top.

Wires went out the back of the housing once disconnected from the dock light.

You can see the grime and dirt on this fender from driving in the rain. It's crazy how dirty it gets. The tubing support can be seen in the background. Connected to the bottom of the fender with one screw.

Spray foam on the back side of the fender.

Removal of the bolts holding the battery compartment door.

Fender and door removed. When I change the shocks on the coach, this is what I'll do. Also can see the air bags and part number for when those need replaced. You can also see the wad of wire bundled up for the clearance light.

Here you can see the start of digging out the damaged luan from under the exterior of the coach, and some foam still stuck on.

That angle is what the fender screws onto. The bottom screw had broken off, so I drilled that out so I can replace it.

All this got cleaned up as well and I used some bed liner on it. I could spend weeks under the coach scraping all the old bed liner off and repainting. A project for another time.
More to come.