you just need to drain the oil into suitable container, if you are replacing with fresh oil think about replacing the oil filter as well. refit the sump plug, take out the bolts, and remove sump, just take care when removing sump as there maybe oil left in the bottom. refit with a new sump gasket and refit new sump. do bolts up to required torque, refill with new oil, do not overfill. turn engine over for a few minutes allow oil to settle check level and look for any leaks around sump gasket.
billsp, July 2012