!, If you have power at both plugs, then the plugs are ok! the HRS plug on the right hand side, runs to earth... so most likely it lost its earth connection, causing the screen not to work, although the tailgate is bolted to the body via the hinges, this contact is insufficient to allow electrical systems to operate, so, my money would be on a broken earth wire, where the wire cross over from the body of the car, to the tailgate! Pull the rubber boot back and inspect the wires very carefully, broken wires should be repaired by splicing a new length of wire in, soldering the joints, and heat shrinking to insulate... its highly likely that these wires have already been repaired in the past, and now need doing again! repairing these wires can also sort out self parking of the rear wiper problems etc
2, as above, eBay or the dealers, may still have them... Put a little grease on the pin before fitting, this will allow removal in the future, without it breaking again
HTH
Thom