You'll need to power the turn on wire for the factory amp with the remote amp turn on wire. Same one you'll use to turn on your new amp. A standard wiring connector can work. you might want to add a couple wires to it or tap into the other things you'll need. I bought a second connector, pulled some pins and added so that everything was plug and play with my new connector.
Search on a post by Buickman104 about radio for that powering of the amp wire. It's detailed there, including magic pixie dust mod.
Then for the steering controls, look into the Axxess add on. It was super easy and works great.
