It seems like it's been done before:
http://forums.swedespeed.com/showthr...x-Hack-Problem
Sounds like he had it working for a few days before having problems, not sure if the problems were a result of the hack or a problem with the tape module itself.
If you know where to solder on the wires, I think you will be fine, if you can't figure out RUN_DET trick, the method I used will work as well. Basically what I did:
1. Look at the back of the cassette loader, you will see a small black switch that is activated by a spring loaded metal arm. With no cassette loaded, the switch will be depressed.
2. Remove the spring from the arm, and tape the arm down so that it is not pushing on the switch.
3. Power up the radio with the top cover off, and use your finger or a pencil to press the switch. The tape mechanism will "load" even though there is not a tape inserted. Your aux input should work fine as long as you don't push the eject button. Since I know my kid will eventually push the eject button, I disabled it by cutting the plastic pin off the back of it.
This way you don't need to have a tape loaded in the tray, so it makes less noise. The only thing you hear is the capstan roller spinning, which I can't hear unless the music is turned off and the car is not running.