Ok then, as Mikey said, you will not need to drain the oil to change the oil pressure sender, although I'd recommend waiting until the car is cold to do it since you might get some residual oil dripping out and making a mess if you do it when the car is warm. Other than that, it's a pretty straightforward item to change out. Just be careful when removing the wire, as they can sometimes sieze on to the post of the sender and pull apart when removing. Give it a couple of good twists first and pull it off by holding the boot firmly.