Re: Cuddy cabin restoration
Removing the headliner is a good amount of efforts and hours then you will have the glue removal to deal with before you can even think about gluing in the new headliner which is by itself a project. If the mold/mildew are not out of control, try everything you can to clean it and be assured that this would only be a fraction of the efforts that are required for a complete replacement.
Rent (or buy) one of these portable carpet cleaners (such as Bissell Light Green. Start with 10% to 15% concentration bleach in a spray can (or 3M mildew remover) and get rid of all of it. When you think you got them all, go back and do this all again for good measure, you don't want to be breathing this $!#T.
If this step is successful, you can move on to cleaning otherwise, the replacement is now justified
For cleaning, buy your preferred carpet cleaning formula from Lowe's or Home Depot and have at it.
After you are done cleaning, keep the cabin well ventilated until the headliner drys.