1, Sealing a record is not a hard thing to re-create. Heat shrink machines are readily available to come by. Check that the record sleeve underneath does not have any marks (pen, scuffs, gravy, brew, etc). Records that have been sealed at the factory will be free from any foreign bodies/marks. Ask other collectors whether the shrink should be sealed along the spine or down the centre of the back (usually top to bottom).
2, If you intend the record to be part of a collection then breaking the seal is not an option. On the other hand, you wish to use the record for what it was intended then it may be worthwhile asking the seller to break the seal once the sale has been completed. This removes the need for un-necessary returns. I've seen instances of 30 year old records being delivered "sealed" . Yet when the record has been opened, it resembles a crisp that is wavier (is that a word ?) than a local MP on the home straight of a election campaign.