Do it yourself

Sorry. But a minute after posting the first, overly-long question I realized partly where I'm confused. The GFCI does indeed protect everything in a series, and then if you have a light that you want protected, then you can wire that in paralell off of the series. Everything is in parallel, except for the beginning or end of the circuit? So, now that I understand this (I think), how do I find the beginning and end of the circuit, where it is in parallel that I can wire in the outlet to protect the entire bathroom, master's bedroom, and even some of the kitchen? I'm getting the hang of looking at a localized wire and stealing power from it, but looking at the big picture, I'm not sure how to find the beginning of the circuit. Or, is it not worth it, and I should just put it in series with the fan alone, to protect the fan, and to only work when the fan is turned on, since I don't really need the outlet for plugging things in anyway? To wire in series, I would have just one wire coming from the outlet, and then I'd splice it into the two ends of the cut wire, to have three white wires under a cap, three black, and three grounds? And the load side of the outlet would lead to the switch, and the switch to the fan, and the line side of the outlet go to the cut wire? But it still remains, is it not hard to find where the entire circuit begins and protect everything? thanks! -Bernard