I was leaving work yesterday and noticed that the oild guage said 0 psi. I drove my truck a little longer and the engine started knocking, then it started knocking louder. So I pulled into a parking lot and shut it off and got a ride home. It's a 97 Sierra with a 4.3L. I am assuming the oil pump is shot and needs to be replaced (correct me if I am wrong). Is this an easy process and where is the oil pump at? Thanks for your future comments.