Commercial keg, already tapped with 'party tap'

So, a friend of mine got married last weekend and they thought they should get a 1/6th keg of Blue Moon. They tapped it with a 'pump/party tap' pumping in atmospheric air, but in the end only served maybe 8 glasses.

He knows I have a kegerator (and a sanke tap on one of my faucets). I know that I could just take the keg and dispense from it, but I'm curious about the possibility of purging the air that's in it and replacing with CO2. Will this make the keg stable for storage at room temp, or has the damage already been done?

They've been keeping it on ice, but that's been an effort for them, which is why I'm curious about this. He's already asked if I can just put it in my Kegerator, but that would take up a bit more room than I think I'd like to.

I want to preserve this keg for him so that he can perhaps use it at a later engagement (and I really don't have a huge interest in a keg of blue moon).

Your thoughts?

If only 8 glasses was poured it should be fine. Usually you can get at least 10-12 pints just using the gas to push before you even need to pump. Do you know if he acually pumped any air in? If so, I would just purge, like you do to a corny and them hope for the best. Just drink it quickly