How can I restore grub for Fedora 17?

Luckily the Fedora Wiki covers this topic! Seems you can just reinstall GRUB very easily, just using a live CD.

1. Boot the system from an installation boot medium. (live CD/USB)

2. Type linux rescue at the installation boot prompt to enter the rescue environment.

3. Type chroot /mnt/sysimage to mount the root partition.

4. Type /sbin/grub-install bootpart to reinstall the GRUB boot loader, where bootpart is the boot partition (typically, /dev/sda). (in your case, sda3 perhaps)

5. Review the /etc/grub.d/10_linux file, as additional entries may be needed in the /etc/grub.d/40_custom for GRUB to control additional operating systems.

6. Reboot the system.

These instructions are straight from the Wiki.