I confirm my retail windows 8 pro key works (activated). You need to use the other key during installation and enter a new key (your own) when installation is finished. I guess the new 8.1 installer only accepts 8.1 keys for the new boxed versions. Makes sense.
WZOR specifically included it in the list of stuff he was going to leak, we'll just have to wait some more i guess...
Yep, it comes with your Surface. I imagine you contact your OEM for the update (if there's going to be one...).