OK, well, when I first used Fedora I made the same mistake. The default installation loaded a PAE kernel instead of the regular kernel. So when I installed kmod-nvidia it also pulled in a regular kernel. For your install you probably would have had to load up kmod-nvidia-PAE. What you will have to do to clean up the installation is remove the kernel that came in with the kmod-nvidia driver and reset everything using the old kernel. OR. If it is a new installation, just do a reinstall. The choice is up to you. Since I made the same mistake, I can help you fix it. If this is what you want to do, let me know if you see the grub screen when you are booting up, so we can stop the boot from going into gnome and go directly into terminal.
We can also use the live cd to do the repair. But if you can stop the boot at grub, it might be easier because we can just boot into init 3 (by adding 3 to the kernel line) and work from there.
A default Fedora install sets grub to a timeout of zero so that's why I'm asking if you can see it while booting up.