The owners of this site, IYCNW Home
redid the interior on there 40' perterson designed islander 40. I also with some guience from Eileen redid my interior on my Jeanneau. you can see results etc here
Not sure if personally how good your headliner is, it may in the end, be easier to replace with new vs re use the old.
Finding the headliner is pretty easy, runs $10-30 US for a lin yard that is IIRC 54 or 60" wide< I used abour 40 or 60 yds for my 29'r. And a roll of 1/4" foam to back it on the hull etc. IIRC it was either 50' or yds, yds is ringing a bell more than feet.
It took me about 40-60 hrs for the work on the interior of my boat.