Before starting to replace oil, make sure you have the required tools including a drive ratchet set, oil drain pan and a crescent wrench. Without the right tools, you will not be able to get this job done effectively.
Consider parking the car on a flat and firm surface and use a chain to prevent the wheels from rolling while you are replacing the oil pump underneath the car. Now use the crescent wrench to remove the oil drain plug, usually found in the centre. Consider draining all the engine oil. This can be done by placing an oil pan right underneath the oil drain plug for disposal.
Consider removing the bolts holding the oil pan by using a 3/8 inch drive socket and ratchet. Now empty the oil pan with dirty oil in it and set it aside. After removing the pan, you should be able to see the oil pump. Remove the bolts connecting the engine block to the oil pump. This can be done using the same 3/8 inch drive ratchet. Pull the pump straight down as soon as you remove the bolts. As you remove the pump, the shaft that distributes oil to various engine parts will also come out with the pump. Place the shaft right next to you.
Now clean the shaft with a piece of cloth and consider reinserting it into the distributor socket that can be found right in the centre of the oil pump mount. Place a new gasket onto the new oil pump and put it back into the shaft to restore the original settings.
Install the bolts to ensure the oil pump is secure to the engine block using the 3/8 inch drive ratchet. Tighten the bolts if needed. Refill the engine with clean oil and start up your car to check for proper pressure.