" I need to access my original fstab so I can undo my changes and bring our system back online."
Boot your rescue CD.
make a temporay directory
Then mount your / partition on /canary
mount /dev/hdxx /canary (where hdxx is your / partition)
Then use vi (any command line editor will do) to edit /canary/etc/fstab
umount /canary before you reboot or you will have to fsck your / partition when you boot.
Be prepared. Create a LifeBoat CD.