Disclaimer: I am not responsible for any damage done to your Jeep, radio, house or dog. Also, to the best of my knowledge this modification works only with 1996-1998 Jeep Grand Cherokee's with the Infinity Sound System, it may work with other radios too, but I have only disassembled my 1996 Jeep Grand Cherokee Limited Infinity Radio.
Sorry for the large pictures. But on the other hand, enjoy the quality!
Start by removing the radio from the car. Remove the volume knob, simply by pulling it off. It slides onto a post. Then follow the instructions below.
With the radio removed from your Jeep you can begin the disassembly process. Remove the 4 screws that hold the front black plastic faceplate on.
Before removing the faceplate you need to remove the equalizer buttons. They remove the same way that the volume knob did, by pulling up on them. Then, gently pry up (with a small screwdriver) the black plastic tabs which snap the front faceplate onto the radio, while at the same time applying a gentle pull on the faceplate, so as the tabs clear their holders, the faceplate will slowly come off. Be gentle with the tabs. They were brittle on my radio and I regretfully broke 2.
Now would be a good time to spray the equalizer potentiometers with an electronic cleaner of some sort, because if yours are as dirty as mine were, they only worked in one location and the lights on them didn't work at all.
So far, this is what your radio should look like.
If so, continue, if not, go back and make sure everything is removed correctly before proceeding.
Remove the 2 screws holding the top metal cover on the radio.
Remove the cover by any means necessary. Be careful, there are tabs which snap in near the front of the radio that would prevent you from prying from the front. Unfortunately I cannot elaborate on the removal, I just sorta pried mine off from the back since I was unsure how it was attached.
Remove the left side heatsink, which covers the circuit board we are trying to access. The blue screws are shorter screws, they are the same length as the ones removed from the top cover. The red screws are longer and need to be reinstalled in the correct location.
As of now this is what your radio should look like.
The 2 red wires and connector pictured below are the wires you will be splicing into for the auxiliary input.
Another disclaimer: somehow I ended up with 2 extra screws, the shorter variety. However I disassembled further into the radio than this write up will go, and I believe I covered all the steps of the necessary disassembly, without missing any screws. But, you've been warned!