You have to prove beyond a reasonable doubt that the account is yours.
Address's on file,
Last 4 of CC (and any other cc's used on there might be requested)
Serial number if the game wasn't purchased online
The same email the account was opened with and so on.
If you petition, they will let you know exactly what they require for the change to be made.
If you make them doubt you in any way, they will not help you. And I don't think you can do the petition in game. I believe it has to be off the website. (which is one way of proving it's your account)
If you do this, would you post and tell us what they requested for future issues such as this? it would be good to know because as you saw, info was from 10 yrs ago.
I wish you luck!