As Spin_bowler says, the changer is in the boot, lift up the carpet on the passenger side and you'll see the changer.
What exactly do you mean with "dash"? The COMAND display will show you details of the station you're tuned in, as will the cluster display. Obviously, both for COMAND and for the cluster, what is displayed depends on which system you have selected and the cluster and COMAND displays can be operated independently, so for example COMAND could show the radio screen while the cluster is showing the trip computer.
Use the COMAND buttons to select a different system in the COMAND display and the steering wheel buttons to select a system for display in the cluster.