If you are talking about the PH headliner, removing the panels also disconnects the canvas from the top. I re-worked mine with thin strips to mount the canvas so that the headliner can be removed without too much stress. If you do one headliner panel at a time it should be manageable. Having the entire canvas removed could potentially be a PITA by yourself; this is probably an understatement...
See this page for the strip mod:
I would use butyl sealant wherever possible.
Re-doing the old butyl sealant is a good idea as you'll have most of the bolts out anyway to access the headliner panels.....and if you are doing the sealant, you may as well change the fasteners to stainless as they are cheap enough....
FWIW, Mcmaster also sells butyl sealant in rolls