How can I safely buy gift cards on craigslist?

I have noticed a lot of people selling gift cards on craigslist at BIG discounts. For example, someone is selling $900 worth of gift cards for lets say $500. I would really like to jump on this but I have foresee some big risks, maybe you guys can come up with a good strategy? First, how do I execute the initial exchange, in other words, I am very weary of handing over cash to someone just to see them run off with it. I guess we could try to exchange at the exact same time but still. Could I possibly have a store employee do the swap for us? Or maybe even try to do it in front of a cop??? Second, even if I get the gift card, its still possible that it can be redeemed online before I have a change to use it, is it possible I can just buy something immediately, then return it for a new gift card? Third, how do I know that the gift card hasn't been issued using money from a stolen credit card? I figure if I just use it up immediately there would be no way for them to find me if they later discover it was a stolen credit card that was used to issue the gift card. Does this make sense? Also, I don't really need $900 worth of stuff from Best Buy, would it be possible to try to get people in line to use my gift card in exchange for some cash, since I would be willing to charge them less than the purchase price? They would still end up with a receipt and everything. Any thoughts on this guys? I would love to take advantage of some of these deals, just wanna take every precaution possible. Thanks.