give reg number to motor factors for correct oil and filter, put car on axle stands, undo plug at rear of g/box and empty oil into suitable container, dispose of at local re-cycling centre, helps oil to flow out if engine warm, when all oil is out, re-fit plug, and change oil filter, beware of oil coming out of filter,put smear of clean oil around filter seal and refit hand tight.refil g/box with correct amount/type of oil. run engine for 10 mins, allow to setle and re-check level.
hope it helps
August 2010