Ok...here is the easy way to change your hostname...this script has been tested on plesk, ensim, plainredhat, and even cpanel servers...but should work on most any redhat linux cp.
***Please note....it is advisable to ensure that your choosen hostname resolves to your server before continuing
1) login to your server via ssh
2) su -
3) wget http://ezsm.net/hostname.sh
5) sh hostname.sh
6) answer the questions
7) done.
For more information on this script, including step by step for the plesk reconfigurator, please:Click Here