Neighbor was in similar situation ... set him up with local mechanic who still knew how to work on vehicles with zero electronics (his own mechanic wouldn't touch it) ... then took him down to local propane dealer and had the propane system inspected/filled.
Consider new batteries (Costco), replace interior light bulbs with LED (lots of threads/links on that subject), and take some time to look for threads on replacing converter with modern/smart converter (less than $200).
Agree with other comments .. get fluids changed (brake, transmission, radiator, oil, etc) and have brakes inspected. Should also consider having tires unmounted and inspected by dealer (RV tires rot from inside out).
Might consider spending a $100 or so and have the rig pressure tested to spot any potential roof leak issues.
Hope this helps.
Kevin