Been there, done that!
Welcome to the forum! :)
I rebuilt an 81 Citation TT from the frame up, replaced and rebuilt the entire thing. I gutted it completely, disconnected the walls from the floor in stages, replaced the entire floor sheeting with 5/8" T&G plywood, replaced about 80% of the floor joists, 100% of the walls including all new paneling, 100% of all the partitions, cabinets, all framework and paneling, 100% of the entire roof and more.
I figure I had close to 1,000 hours into it before I put it aside and eventually sold it for a fraction of what I had into it.
A lot of work to do it right. And you should have an inside shop to do it. I did mine outside in my driveway. What a pain!
You will never ever recoup your costs and labor.
Only do this if you want to, for the love of it. After all my time, effort and money, I still had a 1981 Citation.
I built a website for my rebuild and had it all posted beginning to end. Many hundreds of pictures, along with descriptions of everything I did. Website went down so many times that I finally let it die. I still have the old computer with the website on it.
I also still have all the pictures of the entire rebuild.
I'm happy to share them with anyone who wants them.
Would I ever do it again? No, not a chance, I'd rather spend my time camping.