He still has his pin attached to his acct, its not locked, do you know him? he could call his carrier to release it. You could also use the manage internet email icon to remove the email address and enter yours i *think*
you have to contact the seller, tell them to call their carrier and have the "release" the pin, make sure to include the pin number in your message...once he does that, you call your carrier and have it registered under your name, then resend service books, and you will be good...
--e-mail seller to call carrier to release pin
--call your carrier to register IMEI and PIN
--re-send service books (use search on the forums there are good posts on how to do this)