My thinking would definately require that the ledger be bolted directly to the walls studs. I would definately remove the stucco and the panel insulation. You will get a tighter fit and one that will not cause water to get inbetween the stucco and the ledger to eventually rot out and cause problems.
I will research the intricate flashing and channel flashing methods to make sure I have this correct.
This will be your most important area to shed water. A poor construction here will cause major problems with your home later down the road.