I have some bad news for you. There is no exterior plywood or frame or wall studs. Those sidewalls are vacuum formed under pressure and the interior paneling and exterior fibreglass is formed and glued to a substance that is probably a sawdust and glue mixture. Once water intrudes, it basically dissolves. that is why the fibreglass comes unglued. Repairing is very expensive and basically means replacing a new wall. There are kits available to repair by replacing the interior components with wood. It is expensive and difficult. Good luck.
