Brian, here are some things to remeber when purchasing on eBay:
1) Never send cash in the mail - find another method.
2) Let these folks know that if you don't receive a timely response you will be forced to leave negative feedback. If they are even half serious about selling on eBay they will respect your request for confirmation of your order.
3) Read the seller's feedback BEFORE you bid.
4) Find a few good sellers and stick with them.

Hope this helps. Joe.