I always assume for the most part that a given gun has potentially been ruined internally, regardless of what the seller says about its condition (because for a start they may simply not be aware of any issues, even brand new guns can have major faults out of the box)
Cynical i know, but unless i've actually held and shot the thing it feels better to stay on the safe side.
That said, given i'm almost guaranteed to completely replace the internals anyway its not too much of an issue.
If i were to sell though i'd be as open and honest about it as i can, because i do tend to have a bit more faith in sellers who openly admit when there are faults in what they're flogging.