The best way I've discovered to find that out is to tear it down to that point. I've never done one myself, but I'd say 99% of the time, I've been able to make do with what I've got, or make the "tool" myself. Once you know exactly why you need that tool and or bolt, you can figure out whether you need it or can improvise.
that's what I usually do but, taking it from someone that has already done it helps too.
