nope. you don't need to reinstall fedora as of now... try:
rpm -qa |grep <kernel source name>
this will show whether the package by this name exits...
now, if it exists... rpm -e <kernel source name>
if it shows any dependency problem, then remove that package first...
also, you can type.. rpm -e <kernel source name> --nodeps
to ignore dependency issues. be WARNED that is Dangerous...

next, mount the cd that has the source rpm and then,
rpm -ivh <kernel source name>
next , after successful install of the kernel source, goto ctrl-alt-F1. there log in as root
next type -> init 3
now, press ctrl-alt-F7 to clarify that XServer is not running..
now.. if you have the default kernel provided by fedora, then type,
export CC=gcc32
//NOTE: without this installer may give error.. as there is GCC3.3 present in fedora and the default kernel has been compiled using GCC3.2
then,
./NVIDIA-Linux-x86-1.0-4496-pkg2.run
from the directory where the installer is there...
next.. modify the /etc/X11/XF86Config file to have
Driver "nvidia"
Option "nologo" //<NOTE>this is optional if you don't want NVidia logo
now, type.... init 5
your XServer should start...

ATB, keep posted with the results..