Let me put it to you this way as a former Powerbook board design engineer: there is pretty much no way you will get your hands on Powerbook schematics unless you a) know an engineer or certified Apple repair person (I don't even think they have schematics anyway) who wants to get fired, b) you dumpster dive and have the patience to tape together severely shredded documents, or c) you have access to Apple headquarters. I'm guessing you don't have any of these things. Trust me, you're not going to find schematics anywhere.
Steve
P.S. And please don't ask me for them either, because I won't give them to you. No offense, I just don't want to get sued.