Nothing wrong, just owerwriten the grub stage 2 or MBR
Nothing to worry about.
Do the following(type this in line by line).
find /boot/grub/grub.conf (whichever gets you results.)
You should get a result in form of "(hdx,x) where x is a number"
(type in the correct x you got from find command)
(again, whichever gets you some results)
(this should print the content of your grub.conf file)
You will see some lines
title=Red hat 8
kernel bla bla bla
initrd bla bla bla
You have to type in the lines kernel and initrd under redhat 8
one by one
and after that type in
That should get you into the Red Hat 8.
Once in there su to root and type in your root password. And finally run
/sbin/grub-install /dev/hdx (where x is the drive you have rh8 on)
Now you should see a grub menu
However (you should write commands into grub, to get you familiar with grub) you can just put in your Fedora CD 1 or Red hat 8 CD 1 and boot from that and only continue from su-ing and running /sbin/grub-install
Hope you get it right. And happy Linux use.