There are some classic tricks with paypal and wester union. western union more so. My advice, stick inside ebay rules, which is dont accept and bids unless they are official, that way you are protected...
I have been stung by both a Western Union and PayPal scam, and its just to easy, and means i accepted it outside ebay t's n c's, they didnt care or didnt want to help...
They always offer stupid high figures too, and always come from foreign countries. If it looks to good to be true, ie $500 for an item that usually sells at $200, then it usually is to good...
Tips when sending, always use recorded delivery so it can be traced, and always get the cash firm untill you send. With PayPal this is easy, with western union, make sure you collect the cash, rather than dispatcing when you get the payment note.