Zaffy-T

Bought an insignia a month ago with the low oil pressure warning. Got the seal replaced and all was fine until yesterday when after 80 miles the low oil level warning came on. Immediately stopped and checked and there was plenty of oil. Started the car and the warning has gone and not come back on again. Checked the oil this morning and it's still got plenty in. I've read it could be a sensor issue, just wondering where the level sensor is and how easy is it to change. Thanks