I have learnt my lesson with eBay also. the thing to remember is ask as many questions as you can about the item, and when something says "as is" It is usually a piece of crap. Ebay will probably do nothing as you just assumed the item was working and didnt ask the question (fell in this trap)
My advice to you is: If you paid a big for it, try and get the CD insert looked at by a stereo system place. if you got a bargain..REPLACE THE HEAD UNIT AND RE-SELL ON EBAY "as is"
**Working PART-TIME for Carjunky for a while, Please bare with me =)**
Going for GOLD in Beijing