An 853 frame should have a 27.2 seatpost. I would remove the bottom bracket and seep some WD-40 and/or PB Blaster into the seat tube while keeping the frame upside down for a few days and then try to remove the post. Clamping the post in a vice and twisting the frame carefully has worked for me after a lengthy oil soak in the past.
As to the paint, if it is very bad I would send the frame to Waterford to have it repainted. If it is not so bad you might be able to
buy the correct touch up paint from them as they specialize in restoring Paramounts of every era. If you don't care that much you could probably find a decent match at a hobby store.
Post some pictures please.