01' Replacing Fuel Level Sending Unit

Who out there has some experience in changing this part? Isn't the fuel pump and this sending unit one single part and they both get changed together? I've heard conflicting stories on it and wondered if anybody knew for sure. My fuel guage needle is all over the place and I have a check engine light-the code is for the fuel level sending unit system. I hope changing the sending unit fixes it, I suppose it could be wiring or something else in the system. Who knows? Is there some checks I can do at home on the wiring to isolate the exact problem, perhaps by checking continuity, volts, or ohms? :eek7:

depending on how you buy the part you can either get the pump or sender aftermarket or the whole unit from ford (reccomended)

TECHNICALLY, they are two different parts, but TECHNICALLY, the fuel sendor attached to the same piece as the fuel pump, and some people reference them as a single part.