what gearbox are you running?
warm the landy up before you drain the oils. hot oil flows free'er and carries **** out with it when you drain it. buy the 5litre tubs and a 1 litre tub, transfer the clean fluid into the 1 litre to fill your axles/boxes. remember to clean off the metal bits from magnetic drain plugs and the filter in the gearbox. clean around the filler/drain plug on the diffs 1st before removing any oil. keep everything clean.
I think from memory you need around 3L for each axle, just over 2L for the tranny box and closer to 3L for the main box. dont quote me on this though. But if you buy this amount, you will have plenty.
If your running an R380 main gearbox you may want to use MTF94 over the other stuff recommended.
G