Don't quote me on this, but I'm pretty sure if you just remove the
from your /etc/grub.conf it will just go back to the default. At worst, that in combination with
yum remove kmod-nvidia
yum remove akmod-nvidia
yum remove nvidia-xconfig
ought to do it. Keep in mind, however, that I'm a relative newbie at this too. 126.96.36.199-70 (as per normal kernel upgrades) wiped out my nvidia completely, so I'm just booting the previous version (188.8.131.52-67) for now.