On my PBG4, I found 3 wires attached to the upper case - red and black wires that run to the power button, blue and black wires that run to the mic, and a flat orange cable that runs from the trackpad to a socket on the motherboard. The coloured wires are taped to the upper case, and don't need to be removed. The flat orange connector is directly under the square opening in the upper case, and has loop to help in removing it from the motherboard (which needs to be done). This step was not tricky at all.
