Most of the systems can be tested in your own driveway.
Oh wait, you're in New England and it's November...
It's a little late in the year for working in the driveway and ripping things apart.
IIWM, I'd be hightailing it out of there and heading to AZ. You might be roughing it a little bit while you get across the country but still.
Once you're out of the upcoming cold weather and with all of us at Q, the systems can be tested and parts replaced with a few expert supervisors watching carefully to make sure you're doing it right....
Q also has the big RV markets where you can pick up most of the parts needed at probably much lower prices than you'll find at your nearest RV dealer or they can be ordered in from Amazon etc.
As to the fridge, it's always going to need to run on propane if you're not on shore power. None of the 3 way fridges were ever designed to run on 12V except as a temporary measure while driving down the highway so no, solar for the 3 way fridge isn't likely to work well.