Nine times out of ten the shuttle valve switches are serviceable, the fault usually lies with the two pin connector inside the ABS Modulator, and not with the connector on the SVS plate.
The modification usually refered to as "Option B" bypasses those connectors using a couple of external wires.
So, the chances are that even replacing the SVS switch plate probably won't cure the problem.
As far as LR are concerned, the mod is unofficial, they'd rather sell you a new ABS modulator.
I've done the mod on a couple of D2's with no adverse effects and no more 3 amigos, until a hub fails.
You can easily test the switches with a multimeter set to read k ohms. Connect the meter probes to the two pin socket and you should read 3k ohms. Press either switch and the reading should drop to 2k ohms. Press both switches together and the reading should show 1k ohm. If the switches check out and meet those conditions then it looks like the mod is needed.
There's no need to remove the ABS modulator from the pipework, just unclip the various pipes from the bulkhead and there are two or three plastic clips holding the pipes just below the unit which when they're unclipped you should be able to carefully lift the modulator unit away just high enough to gain some access, albeit a bit restricted to the three screws fastening the SVS plate. I found it easier when I had another pair of hands to hold the unit up while I did the job.
I've attached the details of the mod "Option B" below.
