could help a little with the wires! just fitted one onto my fiesta!

right on the lambda sensor the 2 white wires are for the sensors heater then the other 2 will be a feed and an earth i think, i only used a 3 wire lambda sensor on mine!

on the gauge, the red isd switched live, the black is earth and there should be i think either a purple or blue wire on the gauge, this is for the feed from the sensor!