How do I change the fuel pump on my Chevy G20?

I have a 1995 Chevy G20 van with a 4.3 engine. It suddenly will not start. I took it to the store the other day and came home, parked it, and later tried to go to the store again. It was running fine. But it just turned over without starting. Battery is up, and plenty of gas in tank. I think the fuel pump went bad. How do I change it out? The engine has 204,000 miles on it. It has been well maintained and oil changed regular. It's never acted up like this before and has always been dependable.