I am looking at buying a new Duramax in the next couple of days and have a question about the factory Navi options. The truck I am looking at says it has "touchscreen navigation w/cd, multimedia navigation". What is the difference in this and the "DVD-based navigation"? Does the multimedia navigation work in the same way as the Pioneer AVIC 900BT as in you can listen to music and the navi program will kick in when a turn, etc is coming up?? Looking for clarification here.