I don't know if this is what your looking for but....
When you first start the game up go to Profiles...
Add a new one (can't delete the old one till you have a second profile)...
Name it what ever you like...then delete the other profile....
Is this what you want?
Edit: Opps no that didn't work for the multiplayer name...hmm
I'll tell you this though...the live servers haven't started yet so make sure to change all your names in SD/IMPULSE to what you want it to be so when you log in the first time on the new servers it will register that new one.