DO NOT SEND ANY MONEY. I may be giving away me profession here but........... I deal with issues like this all day long, every day.
I have seen it hundreds of times. When he says the owner is pissed, he is hoping that you will panic and send the full amount right away. I guarentee you this 3rd person does not exist. It is one person, and what he is doing is fruad.
Unfortuneatly, before any crinimal investigation can be intiated, you would have to be a victim. Don't do it. That means you would have to let him cash a check, then file a fraud report with your local law enforcement agency. DON'T do it. Because less than 10% of fraud cases get solved, and less then 10% of the solved cases ever result in any money being repaid.
The reason he doesn't want the $500 paid with PayPal or a credit card is because he wants to be able to disappear. PayPal and credit cards makes that harder, not impossible, but harder to get away with your money without a trace. Paypal and credit card companies have long drawn out ways for you to reclaim your money.....you cant reclaim your money with a check, or at least it is MUCH MUCH harder.
The winning price on that car seems to good to be true any way, and anything that seems to good to be true, most likely is. Most fraud victims think that they found the deal of a lifetime, and they fall for it. This ebay add is most likely a picture of a Viper that is not his, with a too good to be true price, and I guarentee you are not the first one he has done this to.
He wont give you an answer about when, where, how to meet up (or buy your palne ticket) because he wants your money sent to him, not delivered in person. That way you can not put a face to the criminal.
Hope this helps......