To be honest, you won't see that money.
PayPal will reverse it to him, there's no chance you'll win it. By the looks of it, it's an unauthorized claim, and judging by the way you've posted this and the scenario, it's safe to say that there's no way you'll see that money again.
Sorry for your loss man, PayPal isn't safe for people who aren't very trustworthy, next time go through PlayerAuctions and other Non-Chargebackable forms of payment.
If you have questions about this in the future, contact any larger seller/buyer, they'd be able to give you more insight, and possibly purchase your gold off you safely.