From Fedora Project Wiki
Step by step tutorial for installing KDE and removing Gnome:
- log in as root via su
- yum install @kde-desktop system-switch-displaymanager kdm
- system-switch-displaymanager kdm
- reboot your machine
- log in and be sure to choose KDE as session
- if you want to remove GNOME continue, otherwise you're done now
- you can now yum remove @gnome-desktop . Watch out that this doesn't remove any programs you want to keep!
- you should be done now