Mine rusted from the inside out on the two metal lines on top of the tank. There is no way to get to it without dropping the tank. I guess in the Northern States that use salt on the roads or if you live close to the oceans, the tanks rust from the inside out. There is a small piece of sponge that you put over that area to stop the rubbing. I figure it doesn't help that much since mine had slid completly off. If we can get another 19 years out of this tank that will be real good.
I would suggest that you get all of your parts before you take the tank out, if you can wait. Our's was leaking very bad and the fumes became to strong to endure and it get's a little risky having gas dripping down on the exhaust.
If you need the S pipe, get that and put it on before you put the tank in, it will save you from silver soldering it from under the car. Also get the right lock nuts for your drive shaft. I think if I would have had all of the parts (right ones the first time) it would have been a long day's job with a person helping. By myself, as I did it, would have been two days with lots of breaks. Have fun.