Hm, I tried a PMU reset and that didn't work. The battery is fully charged (though it was charged through another iBook). I don't want to take it back to him because I'm afraid he'll mess it up again.
I have a new problem though! If the iBook is turned off and I open the lid, it powers on (way before actually pressing the power button). When it starts up and I barely start closing the lid, I get the shutdown/restart/cancel prompt and it usually shuts down on its own. I'm sooo confused. 😕
It's out of warranty so if I need to open it up myself to adjust any connections, I wouldn't mind.