I was lucky enough to get an Alpine stereo that my brother-in-law was not using any more. Thanks to him I now can play my iPhone through my car without any problems. It came with the XM unit but since I don't pay to listen to radio I'm not installing it.
Installation:
Installation was a breeze. It was one of the easiest installs yet on the Ridgeline. I ordered the wiring harness and the antenna adapter from Crutchfield and found a really cheap site that sold the Metra dash kit. The harness and adapter came first as expected. I soldered all the wires using the directions from the stereo and the wiring harness. It was fairly simple since the wires were all color coded exactly the same. It even had a dimmer control wire which I hooked up. It also needed an antenna adapter since the Ridgeline doesn't use the standard antenna plug but a plastic connector instead. Once all the wiring was soldered, I wrapped each wire individually with electrical tape and then wrapped the whole bundle of wires with the tape.
So now came the 5 day wait for the Metra kit. It finally came today and I started that install. It came with some plastic brackets that needed to be bolted to the upper part of the kit. This was for the lower part that contains the hazard light switch and the flip down storage area. One thing that I noticed was that the storage area door that flips down actually has a lock that engages with a weight that is pushed when the car is braking. Pretty cool. So after getting the cage that came with the stereo into the kit and putting on the brackets, I used the dremmel tool to cut a hole in the compartment below the stereo so that I could pass the USB cable that came with the stereo. This is where the iPhone will be hooked up to play music.
Next was the taking off of the dashboard. This was much easier than I expected. You start at the bottom of the steering wheel on the right and left where there is a notch. You place a small screwdriver in there and pop the clips. Once those are taken off you can use your hand to go around and take off the remaining clips. After this you have to take the slew of connectors for the buttons off the back. Another thing to note is that the dash trim will not come off unless you have the shifter all the way down and the steering wheel all the way down as well. This was hard to do since I had already disconnected the battery and couldn't shift down. So I connected the battery and put the car in low with the key in and disconnected the battery again. Then the dash trim came off easily.
Pic of slots on the bottom of steering wheel
The stereo came out after taking off the 5 bolts and disconnecting the two harnesses - radio and antenna. Then I installed the stereo in the dash kit, passed the USB through the hole I cut, and connected the radio harness, antenna plug, and hazard light plug. Once the whole thing was screwed in, it was just a matter of putting all the connectors back on the dash trim and clipping back in. I recommend hooking up the battery before clipping the trim and testing all the buttons. I forgot to plug in the dome light switch and had to unclip the trim again.
Dash trim off and all plugs disconnected
Stock stereo w/ trim removed
Stock stereo out
Aftermarket stereo with Metra kit installed
Hole cut with rotary tool to pass USB/iPod cable through
Dash trim off and going back on
And finally - installed and working!
After it was installed I checked that the front/rear fade and right/left speakers worked by using the stereo to isolate the speakers. Everything checked out and the nicest part was when I turned on the lights and the display dimmed automatically.