Buy the book by Don Casey on deck repair, which covers all the basics, although he does not mentiont the latest honeycomb coring material (very effictive, and not too expensive) which you should try to track down at the local boat yard.
For what to do with the headliner once you are done, search the archives here as there are a lot of pictures of successful projects.
Gareth
Freyja E35 #241 1972