You are correct is beginning with the roof repairs, nothing else matters if the roof structure is deteriorating. Next would be the walls, looking for bulges and soft spots.
I agree with Tony, use the google search box at the top of the page to search irv2.com for your subject matter or select the Google search button to search the entire internet.
My opinion, if I know the roof has soft spots I would remove the roof covering and closely inspect the plywood decking, replacing sections as necessary, IF I had a covered work area.
You don't know what you can't see.
Please ask all the questions you wish, that's the whole purpose of irv2.com; helping one another with a common goal, leisurely, relaxing RVing.
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