2 hard drives in a laptop? Sata in a laptop? Interesting...
Unlike lilo, you don't need to reinstall grub every time you make a change to the config file. There often is a grub.conf, but I don't see it used very often. The real settings are stored in /boot/grub/menu.lst (in most distro's that I've seen).
But to address your problem: There are a few ways to go about this. The easiest is going to involve your installation CD. It's been a while since I've seen a Fedora install, so I can't be of too much help, but most big distro's have a repair function on the installation medium. Reinstalling grub to the MBR is one of the things that should be available on the CD.
The other way would be to boot the system using a live CD such as Knoppix. Then you could reinstall grub from knoppix or a chroot jail. (using grub-install for example)
Using chroot, you can get knoppix (or any distro) to pretend that the root filesystem is somewhere else. This is useful for using programs and configuration files from your installation. For example (as root):
mount --bind /proc /mnt/sdb1/proc
It's been a while since I've done this (and I'm tired at the moment), so I wont garentee that I'm not missing something, but this should let you pretend that you are running your fedora system from the root account. All of your programs and configuration files will be exactly where they are expected to be, because the system is telling all programs inside the chroot jail that the /mnt/sdb1 really is '/'. This will let you run any fedora specific scripts that you might want to run.
Good luck. Post back. (I might be more help when I'm awake.)