Hey guys, I found a few good threads and diagrams over at JU about this. Some are for a 87-96 XJ and some are for a 97+.
This is the main thread I used for info:
http://jeepsunlimited.com/forums/showthread.php?s=&threadid=331934
Heres a few pics of a 91 FSM overhead console wiring diagrams:
http://community.webshots.com/album/58951859rKpKDa
And another thread:
http://www.jeepsunlimited.com/forums/showthread.php?s=&threadid=383090&highlight=overhead+console
And yet another thread:
http://www.jeepsunlimited.com/forums/showthread.php?s=&threadid=416564&highlight=overhead+console
And another thread (very good for 97+):
http://www.jeepsunlimited.com/forums/showthread.php?s=&threadid=380663&highlight=overhead+console
Anyway, If you want specific info about the 97+ go over to JU and PM jeepzz, I belive that guy has done two or three of those.
For the 87-96 I can tell you that you will need the brackets to mount the console with and you dont have to worry about drilling any holes, if you keep the mount screws from the donor there are indentations above your headliner in the metal where these are to screw into. You will also have to cut your headliner out for these. if your afraid to, remember the rule to measure twice and cut once. And for the wiring, which for me was the beast, there are something like 10 different ones from a harness that plugs into the computer. The wires for the lights are on a 5 pin harness that also plugs into the computer. Keep in mind that if your harness plug shows different color wires as I have seen in other overhead consoles dont worry about them and look at those pics from site two. The locations of the wires in the plug is what is important. They may be a different color but they are for the same thing as what the FSM locations show. Light wires you dont have to worry about but the computer wires are as follows:
2 Black wires = Ground(I ran these to the body for grounding.)
2 Pink wires = 12V+ power from battery(I hooked them up to the 12V+(red) from the dome lite.)
1 White wire = 12V+ switched power(power from ignition, I ran this to the power to my non-working aftermarket power door locks.)
1 Violet/Light Green = Temp Sensor(I ran this from the computer to the front bumper.)
1 Black/Light Blue = Temp Sensor(I ran this from the computer to the front bumper.)
1 Yellow wire = Ground signal to the dome lights(I ran this to the ground(black) for the dome light. Contrary to popular belief the dome lights work by closing a circuit via the door pins and the door pins are located after the lights in the circuit series hence the reason the yellow wire be connected to the ground wire to the dome light.)
The rest are for dimming of the lights, I found them to be more of a PITA and didnt care if the thing dimmed or not.
As far as the rumor of the harness plugs being in the pass side kick panel, your guess is as good as mine. Personally I didnt have any wiring in place and had to run all of my own wires.
Either way, these wires are for the harness for the 87-96 and are the ones needed to have the lights, temp, and compass functional. One thing to be aware of is that if you try to power the computer up while its out of the console and does not have the green tinted glass in front of the display, you will not see a thing as it needs the tinted glas to show any signs of display life.(Ask me how I know this one) If you really want the dimmer to work refer to the second URL I posted for pics of the FSM and save the pics to your hard drive so you can blow them up and read them as they were very helpful to me. Hopefully this is enuff info for yall, but if you have any other questions about it PM me and ill be glad to help. Maybe I should get a write up on this together and post it somewhere for everyone to see
HTH
Mike