Yeh i must admit i was a bit uneasy when i did my first oil change. But for the amount u save its definately worth it.
Waht exactly get done in a big service??
as far as i know its just, oil, filter, check timing, gear/diff oil, and if its a big 1 fuel filter.
The best way to find if something is broke is to break it and fix it later. No point replacing something that had 6 mnths left in it anyway.