I've had to do loads of these,I always start off with a new switch pack,two reasons - first they DO fail and second it gives more chance of a "never fault again" fix. I use a two core wire out through the bottom of the new switch,but I splice the earthing one back into the original loom earth.Cover the cable with the same shrouding,(But smaller) as the original loom,all taped neatly.This way it looks like it came out of the factory like it,rather than having extra odd wires going to obviously non original terminals.
The same fix also works on Defenders....
I do both without disconnecting fluid pipes,with the Defender you do have to be little more imaginative in how you do it as there is very little room.
The most annoying thing about this fix is that I found it on the net AFTER doing 2 or 3 of them under my own steam....