1. the command: umount /dev/hda1 will unmount partition hda1. Wherever / is, is where you would unmount, however: you can't unmount it while using applications from it
My / partition is at /dev/hda3. You can find this by doing: cat /proc/partitions.
I have not used either fsck or badblocks yet as my filesystem is always unmounted cleanly thanks to UPS and some good luck
I'm sure there is an easier way to run fsck, but you could create a bootdisk, boot from it and run a scan while the drive/partition is not mounted.