Pat
You may need to give a bit more detail before you can get a comprehensive answer. For example, you say that the shower is 'wallpapered' - if this is the actual shower cubicle then unless it is a proper kind of wallcovering (as opposed to paper) then it is little wonder it is peeling off.
Most caravan showers are fully sealed - ie they have something like a plastic liner all around the shower cubicle, although some older ones are lined with a heavy duty type of vinyl.
If the walls have been damaged then the panels will need to be replaced - a fairly big job, but well within the limits of a competent DIY person. Your first stop should be 'Wizards'caravan damp web site where you will get an idea of how to approach it. Alternatively you can get a dealer to do the job, although this can be extremely costly (as I found out myself recently)
Your first step though needs to be giving more information if you want the best advice possible. Hope this helps.
