I went from a gas class A to a 5th wheel to a 40ft DP class A and the DP does 45-55 over the Grapevine. The biggest difference for us in a DP class A is the comfort compared to sitting in my truck and hearing the motor for hours and hours on long trips, the DP with air ride and the motor is in the back, the ride and comfort is nice and I don't have to stop every 45minutes for someone to go to the bathroom etc
On one side I say take the old car so you won't have to worry about rock chips etc.
On the other hand the worst trip I ever took was my trip to Utah and I chose yo tow my Toyota highlander instead of my jeep and everywhere I wanted to go I could not and ended up walking because the Toyota had no ground clearance. So if I am going all the way to Alaska I am bringing the jeep.
I had sylvania silver stars I put in a couple years ago which were better than the stock ones but still not good. So a couple days ago I installed these www.amazon.com/Hipro-Power-5900K-Super-Headlight/dp/B003FPF22I
And they are much brighter
I don't recommend electrical contact cleaner , some contact cleaners make plastics and connectors on control boards brittle and may crack or shatter.
When was the last time the heater was used?
If it has been a long time you may need to clean burner orfice and or flame sensor
Other than that everything Old-Biscuit said in earlier post
I carry spare capacitors for the blower motor and for the compressor and just in case I also carry a supco start assist.
If you are changing the motors and motor capacitors you might as well replace the compressor capacitor as well while you have it apart, it is cheap insurance.
I towed a Toyota Highlander with a lube pump for a couple years and still have it as a driver and no problems at all. I would definitely do a lube pump again if needed although now I am towing a jeep so no need