A simple way that will help you with other issues: First install yumex. Sign into a terminal as root (su -) and then type "yum install yumex". You'll then find it under Applications > System Tools > Yum Extender. This is a gui version of yum.
Now, when it starts up, look for the folder and select Desktop Environments. You'll see KDE listed there. Click on it and install. Once done, you can log out of Gnome and put in your username. Then look at the bottom of the screen and you'll see "Gnome" on a picklist. Select KDE from there and boot into it.
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Registered Linux User #362651
Don't use any of my solutions on working computers or near small children.