Did you check the feedback on the sellers? Was it positive or negative? What kind of volume of transactions did they sell? Based on that, you almost have to guess.
People find sellers who sell a lot of cheap parts on Ebay and they are happy with that. I'm not knocking that.
There have been problems with users selling computers where the buyer doesn't always know what he is getting.
There was one case users have talked about where Paypal took money out of someone's account without checking.
I had a dispute with a seller and went looking online and the information to get someone on the phone at Ebay seems to be lacking because they make money through transactions and not through resolutions. When I have to spend an hour trying to find help, phone numbers or email addresses to get help then I know how well their dispute resolution process will work.
The truth is that Ebay is limited in some ways as to what they can do because they can't go to all fifty states and settle things in court. I'm sure they just don't have the money for that. That is why they want your credit card. It seems they just want your money and having their hand in your wallet to settle your disputes.
Ebay's rules and contracts seem to be longer and more available than trying to get in contact with their resolution department. People have created an alternative to Ebay called Amibay because they weren't protected.