Oceana24- My response to your questions. My overall plan was really just use the trailer as is after making some minor repairs and then to make improvements as they popped into my pea brain. That is what I have done.
1. I never planned or saw a need to remove the wall coverings as my cabinets and other interior parts were fine. The wiring is fine. The 120v wiring is copper and even grounded. The 12v
wiring is aluminum but it has not been a problem. The electrical loading on the 12v
wiring is lower now than in the 60’s with led lights and fan motors being more efficient. For example, my original furnace needed about 6 amps to run the fan. My new furnace requires only 1.8 amps. I wouldn’t go into the walls unless there was a real need to.
2. Leave the water tank where it is. The dimensions are about 12x12x48. How are you going to fit this under your 4” floor area?
3. Remove the axle(s) then the belly pan then make your frame repairs. Your skilled team can replace the axles. Lots of information in AirForums about this. Order them from Colin Hyde.