Change server name microsoft server 2012 essentials R2 - Change Server Name

I am installing MS 2012 E r2.

I made a mistake with the server name.

How can I change the server name and disconnect test user
from server and reconnect with correct server name.

Documentation says I cannot change the server name.

If I have to, I will re-install R2.  If so, how do I uninstall and
re-install

Help!!!!

Thanks,

Isaac