Change brake fluid and rubber front brake lines if not done recently. Replace tires if over 5 years old by date codes on tires ( new looking old tires are not safe for RV's)Check engine cooling system including belts and hoses, clutch fan, water pump and radiator. Watch for overheating on long grades. Down shift when climbing or descending steep grades. If house battery(s) and starting battery are old they may need replacing. Check whether the converter/charger is charging the house batteries while plugged into shore power or with RV generator running. House batteries should read around 13.6 volts when fully charged/charging on your digital voltmeter. With engine running, voltage should be around 14 volts. Clean battery connectors and check electrolyte levels, add distilled water to just cover the plates and check periodically. Have propane tank filled. Try running the fridge, leave it on overnight to verify it is cooling properly. Try the furnace and verify that it is cycling on and off properly. Run the roof and dash AC units. Generator should be able to run the roof AC and microwave simultaneously. Assemble a basic tool box with voltmeter, hand tools, mini screwdriver set, adhesives, spare fuses, baling wire, duct tape and screws and nuts, flashlight batteries, etc. Take your rig on a short trip and stay at an RV park while you try everything out. Put up and take down awning, make sure it is stowed securely before leaving. Make a list of things to fix, things to take, etc. Try TV and antenna, stow antenna before leaving. Dump black and gray water tanks wearing latex gloves after you have used toilet, shower and sinks before leaving RV park. (Don't hook up sewer hose and leave dump valves open, waste tanks need liquid in them to drain waste after use.)
Have fun !!! You have a new hobby.