Most LP's bought now have been re-sealed, so I wouldn't worry about opening it or not, I don't think it'll affect it's Ebay value in any way shape or form
I think if you go to
http://homepages.tesco.net/~stoneymeat/ that might help. I don't know who's website that is but it's probably the best one out there for Stoney & Meat Loaf. Hope I'm not violating any rules by posting a link.
Pud