Just started on our first airstream so new to this. I am very crafty and think you can do pretty much all of it yourself, unless the frame is bent or the steel beams rusted out. That not being the case it will just take time and patience to get things fixed up. My frame has pretty good rust damage that caused floor damage. Good thing in a way is that on the 1987 Sovereign
all was original and the rotten floor actually pointed out where the damage was on the underbelly. Once you take the floor off, you can get a good view of what's going on. The forum is full of instructions on how to fix things and really there is not much needed to replace an entire underbelly, just as mentioned time and your own labor. You will need to crawl underneath and yes, be patient. I am done with the floor repairs, cost me about $ 200 all in and now have to take off the old and rusted out underbelly sections, clean up and rust stop the beams, and then put on the new belly. Material costs on 5053 .25 aluminum under $ 300. Lots of drilling and pop rivets.