Fuel Pump?

This post is a little off topic, but since I know there are some very knowledgable people here, and I'm here anyway, here goes. My G/Fs 2000 Cavalier wouldn't start the other day. It'd turn over just fine for a second or two then it'd sound real rough as it was turning over. You could actually see the engine rocking slightly when it was sounding rough. Tried it an hour later and it started just fine, and has been starting ever since. Well, I sure ain't no mechanic, but it seemed like an electrical or timing thing to me. She took it to a real mechanic(hopefully), and he checked it out and said it was the fuel pump. He has one on order. Gonna be $500. total for the job. Does this diagnosis and price sound right?