1) Err, try tuning it on
-- what do you mean?
2) runlevels are used to control what services are started and stopped at boot time and shutdown.
3) "init 1" will take you to single user mode.
4) files are kept in /etc/rc.d/ or /etc/init.d/ depending on your distro.
5) "shutdown -h now" or "init 0" and "halt" works in Suse, not sure about other distros. You can reeboot with "shutdown -r now" or "init 6" or "reboot"
have fun