07 pontiac radio wire harness

Im planning on installing an aftermarket head unit in my 2007 pontiac grand prix without monsoon. It appears to be basic and as easy as any other radio iv installed.
     However, i was told that my vehicle requires a significantly more expensive wire harness with an adaptor for chimes and even data sent and recieved from the BCM.
     Guys please help. What harness do i need to go with?

If you are wanting to keep your chimes and Retained Accessory Power, (The thing that keeps your radio on till you open your door) then you do need the harness they are telling you about. If you do not mind losing those 2 things, then you do not need the expensive one.

Expensive = Metra LC-GMRC-01
Not Expensive = Metra 70-2003

If anybody has any info ie part number and where the least expensive place is to buy it is.....or point me in the right direction like what web site and what is the adaptor called.

Thanks allot

Well its not as expensive as i had expected. My only other question is: will prolonged use of the basic harness (the cheep one) really potentially damage the BCM? The tech i spoke with told me that vehicle data is actually circulated through the radio and the incorrect harness can damage the body control mudule...?
     

     **Do you think ill be ok using the basic harness unitl i recieve the correct one from the mail? Should be 5 days tops?**

Ok guys one last question please. I did purchase the correct wire harness however where the factory harness hooks up to the stock radio there are two plugs one larger familiar looking plug and the other is about half the size. The wire harness I have looks like it only utilizes the larger stock plug. I'm assuming that the box hooked up to this fancy wire harness I had to buy eliminates the need for the secondary smaller factory plug.
Can I just wire up the adaptor and leave that smaller oem plug alone since im using the correct harness?

This is also something I have yet to run into. Looks like a factory aux input probably a several hundo add at the time.