I doubt this will be of use to anyone, but in case you want to know how:
You will need:
- Soldering iron
- 3.5mm male to male cable
- 3.5mm jack
- Electrical tape
- T9 Screwdriver
Take the stereo out. Prise the top off, there are no screws. Unplug the 2 connectors (one on left, one on right) from the tape part to the main PCB. Undo the 4 T9 screws holding the tape part in place. Find the HA12161FP chip. Solder wire from the 3.5mm jack to the following pins on the chip:
This is easier said than done, use tape to help you, and thin single core wire would probably be easier than multicore.
Tape down the wire (so it doesn't move about and undo your soldering) and keep the jack to the right. Put the tape part back on. Plug the cable into the jack, and run it out through the tape slot. Make sure the tape part is in the 'down' position, as if a tape was in there. Pop it back in, and you're done. A better way would be to run a jack down to near where the cigarette lighter is intead of having a cable coming out, but it's more difficult.