Herobrinekills15 wrote a bit on this, and Simon did as well, but I am going to say it again:
Moosevalley STRONGLY suggests you DO NOT change your minecraft name!!!!!
Here is what happens when you change your name:
You have NO access to your protected areas in: PVP, Creative, Survival & Skyblock
The end of the world happens for you basically, and it can be quite a while before Staff+ can get on to assist you.
Bottom line: Not a good idea.