Suggest you use the forum search feature and use delamination as your search word - lots of posts on this subject.
For what it's worth - fixing delam issues is usually a PIA often requiring removal of the exterior panel and repair/replacement of damaged interior. After reviewing the various threads you may come to the conclusion that selling the trailer "as is" maybe the way to go .. depends on your skill base.
EDIT
In reviewing your edit it's clear that your talking about interior rather than exterior damage (not delam). Interior issue aren't much different than your stick house. Consider sanding and putting some wallpaper or maybe a thin layer of luan.