eBay is a minefield. All you can do is cover yourself by describing everything as well as possible and hoping the buyer isn't a scam artist or a complete idiot. However, eBay seems to attract both..
There are a lot of decent, honest people out there though which have made eBay successful - but if you're buying, study feedback carefully. If you're selling - cross your fingers.
I've had people from my own website buy things, then say they are faulty at the other end. They swap out the good part from your product to repair their own, then get you to pay for a bogus repair to what you have sold them. They know who they are - and i now refuse to deal with them, but these are the kind of people who are out there. It's sad, really.
When selling, you could say 'buyer collects' and demo it on the spot - but that will severely decrease the amount you get for something as not everyone wants to travel, especially for a cartridge..
Lee
BeoWorld - Everything Bang & Olufsen