The tractor changed sound and noticed the oil pressure guage showed no oil pressure. There was the proper amount of oil on the Dip stick, drained the oil pan of all oil no water in the oil and noticed that the oil pan plug looked like it has been hit and chipped off a little on two sides. Want to take the oil pan off and need to know what to do next as to repairing the oil pump if that is the problem. HELP.