You have it under the drivers seat.
The manual recommend to change each 15.000miles. If you use good gasoil and never had lighted the water sensor indicator, you could change it at 20.000miles.
Air filter change also 15.000 (depends on driving area) its located ahead of the drivers wheel. If you notice power loss it could be the cause.
Oil its easy to find on the engine left side. Manual says each 3.000 miles but i change it each 7.000 miles since I use shyntethic oil. Mine uses same the that Hyundai H100 because after 2002 both companies are asociated.
Good luck
