You can't use the 'manage' option on an account where the primary email address (the apple id) needs to be verified. When you attempt to use the manage option, you are only presented with an option to resend the verification email and nothing else. If this is the case, you'll have to reset the password to your old yahoo account and then resend that verification email to get access to your apple id account.
Then you can go to https://appleid.apple.com/ and sign into manage your apple id and change the email address. Keep in mind, you can't change the email address to another email address that is already an apple id, so make sure you don't create an apple id out of your new email address.
If for some reason you can't get the password reset on your yahoo account, then I think you might be out of luck. You can try to contact apple and see if the verification email can be sent to a different address, but I wouldn't count on it.
More interestingly, though... how did you get credit onto an apple id that's not verified? If it's from a gift card which has an untouched balance, contact expresslane.apple.com and see if they can transfer it. If the balance has been used in some way, they won't be able to transfer it.
Message was edited by: Imp68
