I've had a few Nikons. Many people find that the original Nikon manuals are not that useful anyway in explaining how the various functions work on the autofocus bodies, and they end up buying a Magic Lantern guide. However, I think you can find what you want here:

Good luck, and remember, no matter how many functions there are on there, it all boils down to focus, aperture and shutter speed. The Nikon F80 I had had what to me seemed like a pretty sophisticated AF system. But almost 100% of the time, I only used and needed the centre focus point, and the simplest autofocus mode it had.