I don't think it should be too bad. I've never changed the fuel pump, but I have had the tank down when I had to change my transmission. You'll need to jack up the rear end, and loosen the straps that hold the tank up. Before you can do that though you'll need to remove the back half of your exhaust, just remembered. Hopefully for you, if there is a god you don't have to much gas in your tank. Another tip is when I lowered the tank on mine, I used I think a 2x6 that was wider than the car, and used the floor jack on the wood. This made it so there wasn't really one pressure point on the tank, it was equally balanced.
Good luck...
Edit: Nice writeup Ray, beat me to the punch!