No need to cut anything open. There are four screws on the underside of the dock for opening things up. The tuner module uses extra contacts on the docking connector for its wiring -- those contacts are not populated, so you would have to order a few (DigiKey), and crimp the tuner connector wires to those, and insert them into the correct slots of the docking connector (from the rear).
Just dangle the connector assembly out through one of the cooling holes on the rear of the dock.
I think the FAQ must have info on the docking connector pin-out somewhere. The instructions for the tuner may also have that info(?).