just saw this 3d now.
i replaced the cracked backlight on my pb g4 this may, so i have seen the insides of this machine. there are also some tutorials on replacing various items in this pb online, screen replacement etc.. the wire that powers the backlight of the screen (the lamp is 2mm thin and runs across the bottom of the screen) passes through the hinge and then under the keyboard past the power button to a small board under the dvd/cd drive.
HIGH VOLTAGE!!!!!! MOVE SLOWLY AND CAREFULLY!
in theory connections can come loose at three locations, 1 - the clip connector (2 wires) where the wire passes by the power button, i assume you know how to lift up the keyboard.
2+3 - a double sided flat wire connector that connects the power circuit to the main board, you have to remove the case cover after removing the battery.