What ever gave the idea you needed root to do that? Now I understand your problem.
First put it name back to what it was, i.e., undo anything you did while running as root.
Second, make sure everything is back to "normal", i.e., your account is running ok again.
Third renaming the account is basically the same operation as moving your account to another drive. Here's a couple of articles on that:
How to Move the Home Folder in OS X – and Why
TUAW Tip: Moving your home folder to another disk (or moving it back)
The central theme here is that you use the Advanced options for the account to change the home directory pathname to wherever that home directory is moved to, or in your case, renamed to. You can do that logged in as root (since it is probably safer than doing it while logged into the same account as the one you are moving/renaming) but you could also do it from another administrator account as well without ever enabling root.