So -- this is what I did yesterday.. I know it looks like a mess and I'll admit that it was a bit of a mess to get it to this point.. Yes, I will be replacing all of the panelling with something -- more than likely both walls will be re-done by the time I'm done (hopefully this coming weekend). As you can see in the wall, there's a piece that's bare aluminum on the inside (left) and the rest has a thin piece of plywood between the wall studs and the aluminum -- not sure why.

It took me an hour to remove the rear window -- 99% of it because of 1 screw that was stuck in place and wouldn't budge.. I had to drill it out and cut the head off. Once that was done I could see the condition of the wood hiding beneath.. Luckily the sides and top plates are in very good condition -- however the bottom plate is completely destroyed on both the left and right sides.. The middle is fine however. But I've decided I'll just replace the entire bottom sill and any other material needed.

So, as I mentioned earlier I was thinking about taking the entire wall apart and that's pretty much what I did.. Here you can see just how bad the corner is and you can also see the stub wall that allows space for the spare tire compartment.. Ever wonder about why there's a piece of carpet attached to the back wall? That's there to cover the bolts that secure the spare tire mount which are visible if you remove the carpet. By the way, the rear horizontal surface is made of 3/4" plywood that is SECURELY stapled to the framing beneath.

The plywood beneath the aluminum on the outside is stapled every ~2 inches to the stud plate (the furthest one back) which made it rather difficult to remove that lower window sill!

There's also a thin triangle piece of wood that runs under the window sill piece to accommodate the angle of the rear wall in relation to the window sill.

Here's what the space looks like between the vertical rear wall and the rear of the LD. You can see the cans for the tail lights below -- luckily there's not much damage that is visible down in the bottom of the false wall.