In my case, when I download a new driver from http://www.nvidia.com/download/find.aspx and try to run it, I get "ERROR: You appear to be running an X server; please exit X before installing.". I comment x startup in /etc/rc.local and /etc/rc.d/rc.local (in my case there are two lines). After the reboot, there is no X server running, but running the driver installation tells: "unload nvidia module". I can't do this with "rmmod -f" because it is in use. GPU monitoring utility might use it. You might want to kill gmond. In my case the following worked:
sudo yum remove nvidia-kmodIt uninstalls the kernel module with the driver. So now the new driver can be installed.