Is there anyway to change my Gamer Tag on the 360 and keep my achievement points?

Yes there is a way but it's going to cost you $10





Click the XBOX GUIDE BUTTON, go to your picture and name and click on it, then click on gamertag and it'll give you an option to change it for 800M$ points





(you can get M$ points by buying them at the store or hooking up a credit/debit card to your account and buying them over the 360)