If you have the Symphony II head unit right now, you won't need to disconnect the Phatbox. When you plug in your RNS-E adapter (which hsould have the wires to support a CD changer) it will work with the RNS-E after configuring it for the right head unit.
You cannot use the glovebox CD changer and the Phatbox together, only one or the other.
You cannot use the glovebox CD changer and the Phatbox together, only one or the other.