Most of the questions at the Q&A sessions with the stars are non-storyline specific--who was your favorite character to play, how did you get your job, how did they do such and such an effect, do you still talk to Jonathan Frid, etc? Most of the "why did so-and-so do what to whom in such and such an episode" come up in the fan panel on Sunday morning. You shouldn't be at risk of getting too spoiled during the Festival. Also, the final episode only reveals the fates of the 1841 PT characters, so if your main concern is avoiding spoilers about the real time DS characters, you have nothing to worry about.
The nighttime movie screenings (e.g. HoDS, The Wolfman, etc.) are always from a videotape with the image projected onto a screen, not from a film print.
ProfStokes