You are standing on a very famous slippery slope. It starts with "as long as I am here..."
The only plumbing that is behind your inner skins should be some of the venting pipes for the tanks, so you should not need to worry about water or waste leaks behind the wall.
The gas lines definitely should not be traveling behind the skins if they are, then some PO has gotten creative/stupid.
The wiring is all behind the walls, but you can check it without tearing the whole trailer apart. Get yourself a decent Volt-ohm meter, and disconnect your trailer from any power supplies (AC power and the batteries), so that every circuit should appear open. If you check each line to mass and see no continuity, then you can feel pretty confident that no wire has had its insulation rubbed through and is shorted to ground. Next, you can check each circuit for continuity from, for instance, the outlet to the circuit box. If you have continuity, then you are good. Finally, check and make sure your AC wiring is not made of aluminum (it should be solid copper). If you have no short to ground, continuity, and copper wiring, then I would say you have no reason to tear out your wiring.
With your floor repairs, the first question is, is your floor rot so bad that you will be replacing entire sheets of plywood, or is it small enough that you can patch it? If you are going to have to go under the wall with your floor repairs, you will have to pull off at least some of the interior skins to get at the heads of elevator bolts and screws that hold the shell to the plywood. This will give you a glance at what is inside the wall. You will likely find old stanky fiberglass insulation, probably with an ancient mouse colony dug into it. If you are lucky, there will be nests and snake skins to go with it, and certainly some mummified mouse corpses. The slope gets steeper from here, as you will either decide you might as well do a shell-off (add 6 months to 1 year to your project), or at least you will be so disgusted that you will want to pull off all the skins and replace all the insulation. Then you will convince youself the wiring may as well be replaced, and you can just add a few more months to the project.
On the other hand, if you don't have to go under walls to do floor repairs (you wish you could be that lucky), the trailer doesn't reek of mouse infestation, and your electrical system checks out as described above, then leave Pandora's Box closed and save yourself a couple years!