I have written a tutorial based on Karanbir Singh's brief instructions regarding CentOS 4. I have tested it and updated it to reflect an install of CentOS 5. In my tests I completed this by installing a full CentOS 5 desktop system over top of an existing Ubuntu system. If anyone tries this or has done it in the past and feels that I left something out - please leave a comment telling me what needs correction and I will try to adapt the post accordingly. All information contained herein should work just fine for Fedora as well, simply change the server addresses accordingly.
I just hope that this document serves to help someone else in the future.