I believe members Norm and Ginny owned a Sunline trailer before they bought their Scamp
, but you probably won't find too many with specific knowledge and experience here, since this forum is focused on molded fiberglass trailers. Sunline is a conventional wood-framed trailer.
Floor rot is a significant and fairly common problem in older units, but techniques for dealing with it vary. If it's in isolated smaller spots and not completed rotted through, there are products to penetrate and strengthen the wood in place. Git-Rot is the one I've heard of, but there are probably others. In high traffic places, like at the door, you may have to replace sections of rotted wood. Sometimes that requires removing cabinets, and then it gets complicated.
You also have to determine what caused the rot- leaking seams or windows
are common culprits- and deal with it.