Remember, you are going up against a big organisation if you try and take them on. They will have some of the world's top lawyers, they'll have far more resources than you too. I don't mean to burst your bubble but I don't think you'll win this one. An old admin friend of mine used to run a site with simply the word olympics in the domain name. The olympic association (or whatever it's called) took him on, even though his site had nothing to do with the olympics, and they won.
Also you can't deny that your domain has the word eBay in it, your site is blatently ABOUT ebay when you enter it. From where I'm looking this can only turn out one way so I'd quit while you're ahead and don't waste your time
P.S. I'm not a lawyer, so don't take this as legal advice