The maintenance interval is 30Kmi, same as power steering fluid. 14mm, 1/2" hex driver is very helpful. I prefer the Hazet 985-14 to the Snap On equivalent. A cheater bar may be required to brake the plugs free, but as mentioned, 50 Nm (37 lb-ft) is the tightening spec. I have reused my plugs even after they were tightened to 110 Nm and have no leaks. For my non-limited slip differential, I use Valvoline 80w90 or Castrol Hypoy C 80w90 - whichever Wal Mart has. The key is GL-5 and something in a 90 weight. For these diffs MB has never approved any synthetics, if you have LSD they you need the MB special fluid.