If you forget your root password, no problem. Just boot the boot/root disk, mount your root filesystem on /mnt, and blank out the password field for root in /mnt/etc/passwd, as so:
root::0:0:root:/:/bin/sh
Now root has no password; when you reboot from the hard drive you should be able to login as root and reset the password using passwd.
Aren't you glad you learned how to use vi? On your boot/root disk, other editors such as Emacs probably aren't available, but vi should be.