1. no idea what your'e on about
2. no, running /sbin/poweroff or such like is fine. you could lose any unsaved work... but that's obvious
3. No it's not necessary, but you'll need to decide which services you don't want to load, and only when you KNOW you don't want to use them, you can stop them loading. eg, if you don't use the linxu mail delivery system, and directly use Netscape Mail or somethign instead, you could remove sendmail and so forth. But the services are generally there for a reason, and you need to be very sure before removing them. You could always make a new runlevel. level 4 isn't used, so you could levae your system intact, and create a new runlevel.... all rather ott just to save a few seconds or so....