Oil pressure gauge problem

What is your question?

My oil pressure gauge has quit working properly. It shows low or no pressure when I am sure the engine is fine. I did check today while looking for a sending unit or direct line to the oil pressure gauge which suddenly started going all over the place (in the low range). The motor (351W) is a new crate motor with only 8000 miles. I was sure it was not the motor because when it was at idle the needle went up and when accelerating it would go off the scale to the low. So I am wondering if I have a sending unit (which I cant find) or a true oil pressure gauge with a supply of oil going to the gauge. I could just live with this but the true oil pressure is important to me. I have really bad eyesite with one nearly dead eye so I am having trouble finding even what type gauge it is. If I cant get an answer I might purchase a true gauge of oil pressure but as of now I would not know where to install it in the motor.