How do you change a fuel pump

A mechanic says, my car needs the fuel pump replaced, The problem started when my car wouldn't start and turn over after work. So I called a tow truck and as the tow truck showed up, an hour later my car decides to start up when I try it one more time. A day later it worked fine in the morning, but died later that day in the middle of an intersection as I was crossing it. How can I be sure the mechanic really changed out the fuel pump in my car and not just a fuse. It cost 700 dollars for the work on the car, and nothing was moved in the trunk of my car. Don't you have to remove the spare tire in the trunk to get to the fuel pump? Thank you, for your help.