My superdrive will no longer read dvds, and it also has trouble ejecting them, I've taken it to an Apple repair man and he said it needed replacing and it would be 400$, but told me if I bought the drive online he could install it for only around 100$. So my question is, where can I buy a replacement super drive for my iMac? I think I want the same model that comes with every iMac just so there is no computability issues when I eventually wipe my iMac for resale. any help would be appreciated.