I agree , pull the harness out and if you want to repair it, its not that hard. Use a multimeter and just ohm out the connections 1 by 1. I did that with my dash harness , i also cleaned the connections and soldered them as appossed to just relying on the crimp on connection. I then used heat shrink tubing to protect the connection.
As for the broken ground, if there is no path to ground nothing will work. If the printed circuit board has only 1 bad path, make a jumper wire to make the connection. the screws that hold the board to the cluster by screwing into the metal housing are grounded. So just make a wire to go across the broken ground from mounting screw to mounting screw.
I have a spare harness that i keep around for parts im sure that connector is still on there. But again if the pin is still in the plug but the wire is broken, its easy to repair. Just use a very small screwdriver to press down on the tab to release the pin . when you get it out gently open the crimp back up. Then strip the wire ,crimp it back in place and solder. Then just push the pin back into the connector.