I spent ages looking for help on the web, so i thought i would condense my findings and installation tips here..
for a video thats similar, checkout http://www.youtube.com/watch?v=hkoglsnQMvo in this case, the vehicle wiring harnesses are different to the silverado in length and location ..but its a good general start..
1. So you knw, the onstar module is behind the a/c controls.
2. Simply "Take off the trim around the radio.." fat chance.. there is nothing simple about it..
a) plastic trim tools wont work
b) get a 1" wide steel rule and put masking tape around it.. go in 1/2 way between the top two righthand clips and prise up... use another tool (wrapped) as leverage so that you can increasingly get underneath the trim. Now read carefully... For these clips, as all the others, you will put so much pressure that you will be SURE that the trim will break, and just before it does, it will pop out. Drink a beer and congratulate yourself... All i could think was "crap how much is this thing?", then "do i really need bluetooth"?
c) Move downwards, popping out each clip in turn.. as you do the last two, on the top left, the whole thing will leap out at you and hopefully not smack you in the face..(yes it did.)
3. Use a 7mm nut driver take out 2 bolts and remove the power plugs and lay to right of console
4. Ditto a/c controls
5. You will now see the onstar unit a grey/silver metal box laying what was directly behind the power accessory bit.. Dont even think about it.
6. Remove the radio (4 bolts). At this point i used a piece of string and dangled the radio up and out of the way (looped around sunvisor bracket).. this is far better than trying to remove the antenna plug and risking the anti theft crap.
7. The onstar is held in with two plastic spring clips, left and right..they are stiff..i used a screwdriver then prised one end up, then the other.
a) the onstar does not appear to come out much.. a tight fit but insert your hand (or kid or wifes hand) far back, grab the loom and p-u-l-l slowly, and you will extract another 4-6" of cable.
b) my truck only had two connectors, remove them, remove the gps input and antenna output and lob the onstar over your shoulder.
8. Install the bluestar
a) plug the two plugs into the bluestar
b) Insert, plugs first on LHS, and use the foam wrapper, folded to jam firmly into place..no it aint going anywhere.. but hey, use something fancy if you want.
c) for PC access, i purchased http://www.amazon.com/gp/product/B004ZM ... 00_details This cable sneaks out the back of the console and leaves a USB female where only rats can see.
9. With all the crap dangling, go ahead...I know you want to.. pair it up and make a call
10. Insert radio, a/c & power accessory strip..make sure they line up vertically
11. put the trim back on..this is stressless and takes 1/100 the time to take the sucker off.
What works..
* button on wheel starts and ends calls
* volume control works
* caller ID comes on radio and DIC (driver information center..i had to look that crap up).. you know, where your milometer is.
* obviously onstar buttons work too
* stock mic settings were good, reported excellent call quality up to 70mph on highway.
So its a success, plan 2hrs, assuming you read this, and have the stuff all at hand.
photos attached..