02 Cadlliac Escalade w/Bose

I have a question in regards to this vehicle as I don't normally have these coming by my install bay.  I did try seaching for an answer and didn't turn anything up, so if there's already a thread about this, I'm sorry and please direct me to it.  On to the question:

I have a customer who wants to do a radio and 4 in his 02 Escalade EXT w/Bose.  He complains his passenger side speakers all simultaneously stopped working, so I'm leaning towards bad amplifier or bad head unit.  I already know it'll use a GMOS to retain OnStar and all that, but my problem is that I don't know what the amp bypass will require.  Where is the factory Bose amp, and how do I bypass it?  Will I have to run all new wires from deck to 4 speakers?

I need to find out so I can properly quote him an installation price and more importantly, so I can do the installation correctly.

OnStar uses the factory amp and speakers, so if you bypass it you will not hear anything from OnStar, unless you want to add another speaker for the onstar to play through.

Factory amp is under the center console, near the back. Plugs are towards the back of the truck.