We are in the same boat, we pulled down ceiling panelling to find soaking wet insulation and some rotten wood too. So, we are going to have to reframe, reinsulate and repanel after making sure all leaks are taken care of. If you only fix the surface, the damage may continue to get worse underneath (and possibly get a nasty mould problem.) Are you planning on keeping your unit for a long time? We are fixing ours up properly so we can sell in a couple years and move up.
My two cents!
Jennifer (John's better half)