Here is the official service schedule -
http://i143.photobucket.com/albums/r159/MantamadGTE/DiscoveryService1.jpg
http://i143.photobucket.com/albums/r159/MantamadGTE/DiscoveryService2.jpg
All quite straightforward, if you are changing the gearbox oil, the filler plug is a large head bolt (32mm comes to mind but I could be wrong) and not that easy for access - I transfer the oil into a 500ml squeezy container to fill it easier.
Be carefull when removing replacing the axle oil filler plugs they are plastic and break easily.
Remember there are grease points at both ends of the prop shaft but only 1 nipple fitted, just unscrew and reposition in the other end (remove blanking screw first)
centrifugal oil filter is easy to get to but main oil filter (if changing) is a bit of a faff.