12 volt outlet

You could keep this discussion all in one post since it is all going to be about 12v socket mod in your trailer, but the answer is.. maybe. The way warranty work works is...

If a mod causes the issue, then yes the mod may affect the warranty on that item. For instance, you tap into the furnace wires, and the furnace goes out.. a dealer MIGHT make a case for the wiring mod being a contributor. might. But lets say you do it and the gas cook top stops working.. non issue. or fridge, or windows leak, etc.

For the most part, Forest River handles warranty issues in good faith.

I just put in 2 12-volt outlets, used 12 gauge wire so they could easily handle a fan or any thing else. I ran straight from the fuse panel so the line is on it's own and fused. It took a little more wire because I ran it from the fuse panel with all of the wires running to the back and used the wire hangers that where already there. Goose

No one is removing wall panels!
 AFAIK they are bonded to the frame in a vacuum process.

Depends on where you want the outlets. If you want a plug in the dinette area you can run the wire around under the seats in the storage area. If you want it in the back by the bed I would run it from your power supply through the floor, bring it up through the floor by the bed. However if you run your wire under the trailer put it into a plastic tube for protection.