Mine a leaking like a good un and its causing problems with the abs/ traction control as the sensors are getting covered. Anyone replaced these? The book of lies says that you need to preload the front one but I have no idea how to do this. Any thoughts?

The sensors are sealed so a bit of oil should not affect them....likely to be a different problem.
Replacement of pinion seal is in the guide.
Drive shaft seals are easier:
Unbolt and remove abs sensor (for protection)
Unbolt driveshaft from hub
Lever driveshaft out of diff with prybar / large screwdriver.
Clean up the mess then lever out old seal and press in the new one (either tap it in a bit at a time, working round the outside with a soft drift or find a suitable tube to drift it in)
Refit driveshaft etc and top-up the diff.