yeah, the 98 has its own fuel pump that isnt compatible with the earlier or later model mustangs. one tip i can give you is make sure the tank is almost empty. if you can, drain it to about 1" from the bottom.
its been years since i changed mine, but go to the FRPP website and look up the instructions for the fuel pump they sell, tahts what i had to use and i remember it worked out pretty good, there were only 1 or 2 things that slowed me down a little.