Regarding the oil level sensor, you are going to have to remove the oil pan to replace it. It is a fairly simple job. I would probably suggest replace the sensor instead of just the o-ring do to the sensor tends to leak internal along with the o ring. When installing the sensor, be sure to install it exactly like the old one came out and ensure that the wire will not get rubbed by the crank shaft on the inside of the oil pan.good luck.