2003 Sienna will be similar to all Siennas from 1998 to 2003 production years to change oil. Perform at your own risk.
Steps are as follows:
1. Park your Sienna on a paved level road (for safety) 2. Press the footbrake (for safety) 3. Open hood and take out the engine oil filling cap and wait for the engine to cool down. 4. Use a piece of wood and place the jack on the wood 5. Jack up the driver side wheel by about 300mm and put a stopper behind the right rear wheel (for safety) 6. Put in another jack near the driver side wheel and adjust both jacks so that both jacks share the load (for safety). 7. Put absorbent (cloth, old newspaper etc) underneath the drain plug (near passenger side at the back of the lowest part of the engine) 8. Put spent oil tray underneath the drain plug 9. Use a ring wrench (13mm or maybe 14mm can�t remember) to loosen the drain plug (beware if the plug is too tight, don�t try it by force or it may set the jacks loose and the car will fall on you! In this case, to avoid risk, don�t try to change oil yourself, take it to the garage) Direct the waste oil to the waste oil tray Oil will be drained in about 20 minutes 10. After oil drained out, wipe out oil on the casing with a clean cloth, replace the drain plug and tighten 11. Move the oil tray and absorbent beneath the engine oil filter (between the radiator and the engine) 12. Loosen the oil filter (you might need a special tool to loosen the oil filter if it was tightened too much during the last oil filter replacement) 13. Use clean oil to wet the seal of the new oil filter 14. Wipe the old oil on the engine. Screw on the new oil filter until you feel the filter seal touches the engine. Hand tighten only � turn or you will have difficulty to get it loose in the next oil filter change 15. Pour 4 liters of new oil into the engine oil filling point with care (not to spill) 16. Cover with the engine oil filling cap 17. Pour used oil into the empty engine oil bottle and wipe clean all spilled oil. 18. Close hood, lower jacks, remove stoppers 19. Release the footbrake 20. Check for oil leaks at the drain plug and the filter immediately after engine 1st start, and after one day driving check for any signs of oil leaks on the ground. 21. Disposed of waste oil, oil filter and absorbent properly. 22. Done.