Well, here is a start:
First you need power to the bags. There is a rubber grommet on each that have some wires going through it. On the right back, you can remove one of the white plugs and push your wire through there. On the left side, I drilled a small hole through the rubber.
Next, you will need to tap into the wire leaving the bag that switches to ground when the bags are open. On the right bag, the wire is white/red. On the left bag, the wire is blue/red. You should cut the wire and splice in a diode just to be safe and not send +12v back into the computer. The bar side of the diode should be pointing into the bag (the other side is attached to the wire leaving the bag). You need to attach the negative side of the LED's (or the timer) to the cathode (bar side) of the diode.
Here is a schematic that will hopefully clear up some of this. And a parts list if you buy through Digikey. Radio Shack may or may not have these exact parts. Some can be fudged (close counts). The bigger the capacitor (22uf), the longer the lights will stay on before dimming off.
The timer is not mandatory. Just ignore it and connect the LEDs right to the power and switched ground wires.
Attachment 3939
Attachment 3938