For either engine option in your car replacing the oil pan gasket takes 1.4 to 1.6 hours. But the oil leak may be due to a leaking rear main seal or other oil leak higher up on the engine. To pin point where oil is leaking from the engine may need to steam clean the engine first. Starting with a clean engine and then running the engine it may be easier to identify specific leaks. If the oil leak can not be identified, florescent dye may need to be added to the oil and the engine run for a while. After running the engine the dye used has florescence in the dye is visable under UV light and it helps pin points the source of the leak. Identify the color of the oil to differentiate wether the oil leak is steering fluid, brake fluid, or transmission fluid and try to identify the location of the fluid leak under the vehicle, ie front of engine compartment, rear of engine compartment , passenger or driver's side of vehicle.