From my understanding the awd system goes through the oil pan itself but I may be wrong and thinking of my buddies trailblazer ss and it was so much fun: (

 

The right side can be done but the left side requires removal of the diff.

 

How funny... I just had this repaired(thankfully under extended warranty) as $30 in parts amounted to $1200 in labor. It sounds like ti is quite the job to complete as they did have to drop the frame and disassemble the diff.