I've got no reason to replace my head unit but I pulled the dash apart today to get a tap for my radar detector. I plan to tap the ignition and ground wire on the head unit to supply power to my radar detector. The wiring will run up through the floor of the NAV compartment. This way there will only be a short distance for the wiring to hang between the NAV opening and the optimum place on the windshield for the detector. Also, it will be very easy to pull the detector off the windshield, stuff it in the NAV compartment, and shut the door. I'll have to finish up tomorrow because I'm out of splice connectors and electrical tape.

Here's how to pull the dash apart because it's not ordinary. The trim around the head unit and guages is integrated with the head unit and guages. They all come out together. There are 6 screws holding this cluster together and a few clips at the top near the guages. First, take the rubber mat out of the NAV compartment, remove the two screws holding the front section of the floor of the NAV comp., and remove. This will expose the top two screws holding the cluster in, which need to be removed. Next, remove the trim around the gearshift. It is just clipped in and you can pull it easily by grabbing the lip of the silver ring that surrounds the gearshift. Just turn this trim piece off to the side. This will expose the 4 bottom screws holding in the cluster. Remove them and go ahead and remove the screws holding in the white module that receives the control signals from the AC/heater/fan. Now you can pop loose the cluster near the top around the guages and remove the single connector that goes to the guages. Now you have to move the whole cluster up towards the windshield and straight out. All that's left holding it in are the connectors to the head unit.

If you want to tap the power supply on the head unit for anything, the ignition wire is green and it's located in the upper left corner of the larger connector if looking at the face of the connector. Ground is the wire just to the right of IGN and I believe it's red. You probably should test these out either with a multimeter or trying to power up whatever you need power for before putting things back together. I test ground with a multimeter by running a long wire from the neg terminal of the battery to the minus side of my multimeter and checking resistance to each of the connector outputs. When I reach a GND wire, resistance will be very low (less than 1 ohm). I test battery and ignition by looking for the wire that has approximately 12V. IGN will only have 12V when the ignition is turned one notch or more. BATT on the head unit connector is a fat yellow one that is on the bottom center and always has 12V to it. Before cutting/splicing wires, remove the negative cable from your battery so that you don't get fried.

Oh, I say the whole cluster is integrated but I'm sure that the guages and head unit unscrew from the trim piece. The screws are just hidden behind the trim piece and can't be accessed until the whole cluster is pulled.

Notes:

If you have a Bose stereo, your wiring colors and placement are likely different than mine.

If you have NAV, it is probably the same procedure but you'll have to remove the NAV connector too.