Is there a way to change your username while keeping the same email address?
I think there is. You think you would need to have GW delete your existing account first though before signing up with a new name, so it might take a couple of days to cycle through the system. I 'think' that would then free up your existing email addy to be used again.
To find out for sure I suggest you contact GW via the Contact Us link found at the bottom of any GW page.
If you find out anything for sure, would you mind updating your thread here?