Not sure what panels you have, but on my 2003 390 the headliner was coming down in the salon and forward cabin. I bought headliner glue in an auto parts store and re-glued each panel one section at a time. I used a squeegee to smooth each section in place. I did not take them completely off as that would have been a major undertaking. I pulled down 1/3 rd of a section at a time. It was easy to do and the finished job looks like it did when new.
John