Congratulation on finding a sweet deal and welcome to the life style.
Knowing the former owners is going to help a lot. Check with them concerning past maintenance which will help prioritizing your list.
Tires are #1 if the date codes are past seven years or so. Then hit the roof seals to prevent water leaks and associated potential damage. Once you are confident the coach will roll safely and not rot from water damage go after the power train. Engine oil, brake fluid, transmission oil, coolant, power steering, belts and hoses (to include the flex brake lines at the wheels) if the former owners haven't done so in the past five years or so.
Maintaining the coach isn't difficult but you just have to make time and do a bit of research concerning technique and material. You'll find lots of info on the various forums, You Tube videos and blogs that owners have posted.
Tiffin has a good reputation with their customers and they might even still have the builders plans and other back ground info for the coach so check in with them. Also they support the Tiffin Allegro Club and there is a separate forum just for Tiffin owners, Tiffin RV Network.
Good luck and keep asking questions, just one at a time. Posting a laundry list of problems makes for confusing replies.
