There are so many things to check with a unit that has been sitting for 5 yrs. First, get a new battery. Second, check out the water system, you will likely need to replace faucet seals and there may be leaks with some of the fittings and the water heater bypass valves. 12V water pump seal may be bad also, but it sounds like you will be hooked to city water, so that is not so important. Before you remove the toilet, pour some soapy water in the bowl and see if the flush valve moves ok, then pour some more water in and let it sit to see if the seal holds the water in the bowl (and odors out). Otherwise, you may need to replace the flush valve/seal.
If you have access to 110v, then check out the A/C, the blower motor may be stuck, with power off, remove the cover and see if you can turn the fan by hand. Same issue with the furnace, years of inactivity and the blower motor in the furnace may be stuck and if it's not running, the propane will not turn on. There is also a 'sail switch' that can stick and keep the propane off.
Very likely all gas jets in the furnace, stove, water heater and refrigerator will need to be cleaned of dust and spider webs. Also check for bird nests and wasp nests that could be blocking the furnace vent, water heater vent and especially the upper vent for the refrigerator (likely a roof vent). No need for an RV fire due to a blocked vent. And likely you will need new propane bottles or at least new valves and recertification. Possibly a new gas regulator, and check for propane leaks everywhere, especially at joints and flex lines.
Replace the tires, even for just a 2 hour trip, since they are at least 5 yrs old. You might find some used tires, just check the 4 digit date code so you know their age. Wheel bearings should be checked, chances are they need new grease. Again, even for a 2 hour trip, a blown tire or a burned bearing is no fun. And the electric brakes need to be checked at the same time to make sure they operate and retract smoothly. Check tail lights and clearance lights, corrosion is more likely an issue than burned out bulbs.
Regarding the bubbles in the interior paneling, you might try popping them with a needle, better yet a syringe filled with glue and then pressing them flat. Then the vinyl should have a special primer applied prior to painting.
Insulating the floor from above is not too practical, although padded laminate flooring will insulate better than new vinyl flooring. If the trailer has a sealed underbelly, then most likely there is some floor insulation. If it is not sealed, then it may be possible to use 3/4 inch thick rigid insulation board. Or just add skirting around it after you move it to the new location.
Larry Day, Texas Baptist Men volunteer
'13 Silverado LT 3500HD D/A CCSB 2wd, custom RKI bed
'11 Crossroads Cruiser 32MK loaded