I just went through this process with my '65 Special Landau. My strategy was to remove as much trim as possible to save time and a lot of money and then have a professional upholstery shop do the actual vinyl roof removal and replacement. Good news and bad news about removing the exterior trim. The good news, the headliner DOES NOT need to be entirely removed, only the portion covering the sail panels up to ceiling. The bad news, a lot of things need to be removed to expose the speed nuts fastening the Landau bars (in my case) and the exterior sail panel base trim. Begin by removing the entire back seat and center arm rest. Then remove the power window controls and side panels. Next remove all stainless side and rear window molding for access to the sail panel headliner staples and fasteners. Then remove the stainless trim and rear package tray. Then remove the courtesy lights. Carefully remove the sail panel headline staples, insulation pads, courtesy light brackets, cardboard inserts and insulation pads (if removed carefully, all the pieces can be reused). Use an easily removed type of tape (I like gaffer's tape for this purpose} to tape the sail panel headliner out of the way. Now you should be able to access all the nuts holding on the trim. In my case, the landau bar is held by four speed nuts (7/16" I think) which have been seated onto dum-dum covered posts on the back of the trim. The lower sail panel trim is also secured by two 7/16" speed nuts and one 3/8" speed nut, different from the others. This bolt is the furthest to the rear and not obvious how to access it. You need to remove the small black panel in the extreme corner of the package tray support structure and then you can get a socket on the nut. Finally, be very careful removing this trim, especially the landau bar which is pot metal and quite thin in places. With the dum-dum on the mounting posts and resistance from the vinyl roof and padding you'll to slowly pry the trim off (I used a plastic
pry tool working as near the posts as possible and keeping and even distance from the roof). I may have missed a few steps and your '66 may be somewhat different since you likely don't have the rear quarter windows, but at least you get the idea or what's involved.