Standard items to replace are oil and oil filter, air filter and spark plugs (or fuel filter if it's a diesel). Undo sump plug (make sure it's not the gerabox drain plug!), drain oil and replace plug.
Remove and replace oil filter, replace air filter element, remove plug leads, remove plugs with a spark plug socket. Fit new ones with a smear of copper grease on the threads, and tighten.
Fill with 3 litres of oil for a start, wait and while, then dip the dipstick. Add a bit more and repeat til it's at the maximum. Replace filler cap.
For fuel filter (if a diesel), remove old filter, replace with new one, pump hand primer (if there is one), then start car with foot on the accelerator, and hold there for 30 secs or so.
Recheck oil level (wait 2 mins or so before checking), then refill to maximum.
John, April 2008