I am sorry, I should have revised my statement above to bose will work 90% of the time w/ the 20 dollar harness, I forgot about way #2, but also I was troubleshooting why my guages wasn't working in my car at the same time I was on here earlier.
There is 3 ways to replace the stock w/ an aftermarket radio that I know of w/ onstar/bose/monsoon.
1)A harness that has about 17 foot of like 14 wires that are 16 gauge, and you just have to relocate the stock h/u to the trunk. That way is easier than it sounds, honestly I have done it in a million times, especially in pontiacs.
2)the part number from metra is 70-2003, it is about 20 dollars and it is a harness for just the radio plug, all you need to do is hook up the power antenna or sometimes the remote turn on wire (both essentially do the same thing, just one wont work sometimes and the other will) to the factory amp turn on wire. *You lose onstar and chimes this way though* If people need the wiring colors I can supply this, it just might take me a day, because I know a lot of wiring off hand, but not everyones.
3)The other way is metra part number gmos-04, and is actually one of the coolest wiring harnesses out there, because it is adaptable to pretty much any grand prix from 00 up w/ onstar and monsoon/bose systems. But anyway it is a straight harness that is solely plug in and go. The only downside is that its over 100, I am pretty sure its about 149 bux. Everything stays functional with this.
James #3 would be your best bet.
-steven-
