Well, you could have them paste the ebay url for their listing and then fetch the page and process it with regular expressions to extract the data you want. I'm a complete novice with regexs so you'll have to ask someone else to help with that part.
You can fetch the ebay page with the CURL functions then you can just process the html for the content you want.
Some of the ebay code has convenient comments like '<!-- Begin Description -->' that you could use to find the info you are after, I'm sure that the rest is in <div>s that you can search for as well.
