Comment 8 for bug 32853

look at the livna fedora RPMs to see how this can be solved ideally (for the user):

"The Livna Nvidia and ATI driver RPMS come with a small python script, which works as an extension to system-config-xfree86. It does all the editing of the Xorg configuration file for you while installing/activating the driver.
[…]
Also, you do not need to drop out of X to perform the installation. And if you boot a kernel without Nvidia support, a boot script will automatically detect that the Nvidia kernel module is missing and revert to Xorg configuration."

http://mirrors.ircam.fr/pub/kde-redhat/apt/svn.livna.org/packages/nvidia-glx/devel/nvidia-README.Fedora
http://mirrors.ircam.fr/pub/kde-redhat/apt/svn.livna.org/packages/nvidia-glx/devel/nvidia-glx-init
http://rpm.livna.org/livna-switcher.html