I'd stay away from eBay but BHPhoto is a very good supplier and Apple authorized.You can save money on AppleCare getting it @places like eBay and bh photo
Ebay has a page on buying AppleCare on eBay:
http://www.ebay.com/gds/Beware-of-Fake-Applecare-Protection-Plans-/10000000017131815/g.html