I also have a 2019 375FL and it appears the way they did the wiring is slightly different than yours.
My thermostat for the furnace/AC and the ceiling fan is located near the kitchen sink on mine. But the 120 v outlet, the tank heaters, the electric plug, and light switches for the slide out and over head are located in the same location as yours.
Here's a photo of mine. The paneling on the side of the upright post (floor to ceiling) on the outside wall of the camper is buckling some in this photo, probably due to high humidity where I'm located right now. I need to get some finish nails and tack it back down flat.
But.... for your purposes, the timing is perfect. In the photo I stuck a slip of paper between the panel to show you, all you need to do to access the wires is remove this one piece of paneling. Use a flat head screw driver, or even a butter knife and wedge it under the panel and it will begin to pull right off.
Do it careful so you don't damage the paneling. Once you have it removed, pull the staples from the back side (straight through) so you won't scar up the front and have unsightly holes. Do your wire fix, and then re-insert with small finishing nails.
Here's the photo. The paper stuck in the wall shows how to remove it. Instead of paper, use a butter knife or a flat screw driver to begin wedging it out and loosing up the staples holding it on.
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History is not about the past, it's an explanation of the present.
2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually