Instructions
Turn on your Xbox 360.
Select "My Xbox."
Choose "Change Gamertag." If this is the first time you are changing your gamertag, you don't have to pay anything. If you have changed it before, you will have to pay 800 Microsoft Points to change it again. The points will be automatically deducted from your account. You also can select "Add Microsoft Points" to add funds to your account.
Select "Enter New Gamertag." A virtual keyboard will appear on the screen.
Select the "Symbols" option on the virtual keyboard. Select the symbols and signs that you want to use for your gamertag from the list on screen.
Select the "Yes, use this gamertag" option to change from your old gamertag to your new one.