The water damage is the real bug bear, depending on initial construction. Many of these campers ( in general, not familiar with the Shasta, but it looks run of the mill) have fiberglass on the outside, some kind of stiffener, often plywood, then luan on the inside. If the water has seeped into the the walls, it could be a total gut and rebuild.
Have you looked for youtube videos yet? I have found the books, blogs, and even some videos tend to skip some crucial step (ie, just remove X, without telling you how to get access to X or that you need a special tool to actually remove it). As such, it is important to do lots of research with a variety of sources, hoping that they cover each others' gaps. A couple of hours