go for it
I am now on my third caravelle, first two were 24 footers, now a 22 footer. I also closely worked on other airstream mainly pre 67.
I find the caravelle (which applies to a lot of later airstreams) a lot easier to do than the earlier airstreams, that is if you want and do preserve the interior. Everything has been put in with rivits and if its still original, meaning as little repairs, new appliances etc put in, you should be able to take the interior out in a day, and put it back in in about a week, including cleaning etc etc.
The moment that you start customizing it will start to take much longer, depending on your tools etc. My 22 footer, I will post pics when done, has taken me 3 weeks of personal work and a other 2 of hired labor. That one has been totally redone, including systems, polishing etc etc.
All had, apart from rot near the water tank, bad floors under the shower. That is the only area which is a bit harder to take out with out damaging the showerstall, but you may want t consider deleting the shower anyway. I dont k ow of anyone here (uk) who actually used their shower.... al campings have facilities better than on any caravan. Turn it into an extra cupboard, drying cabinet, what ever.
The reason for saying do the whole floor is that the caravelle chassis is not necesarily exactly strong and welded well. My three caravelles varied hugely in terms of materials ( width and shape of beams) andwere more badly corroded than pre 67 ones. in two of the three the a frame was so bad that it could have failed and if that happens you ruin your trailer making it unrestorable.
the added benefit is that you will have a chance to really. clean and check the whole caravan.
If its your first project and have no tools, workshop etc....... just do the rotten bit and take of the belly under the a frame to check. You could even consider just taking the front settee out and back, its the easiest bit of te interior to do