As for reprints--I have a Gretzky and Michael Jordan rookie reprint. I didn't buy either of them. They were given to me by a reputable dealer who had a bunch of them. I have them in toploaders and have labeled them as reprints in case I stumble across them some day when I'm too old to remember where they came from. They are fun to look at, but I have a real Gretzky rookie. (I don't have the Jordan though.)
As for warning someone 10 minutes before the auction ends--If I discovered that I had bid on a card that was a fake, I just wouldn't pay. If the seller filed a claim, I would just explain that the card wasn't as it had been described. Or, I could pay and then file a claim with PayPal. I would hate to pay for something that wasn't real, especially if someone could show me that it was a fake card. Just my opinion!