Your User Account page is accessible from the My Geek menu at the top of most pages.
There you can:
(1) You cannot change you UserName. If you don't like your UserName, your main options are to start liking it or make a new account.
(2) You can change your Display Name (first name, last name) in My Geek, Profile, by editing "User Details" at the bottom of your Profile. (Click on the pencil icon to edit the "User Details" section.)
Need new graphic...