It you get the pump at napa, make sure you get the ACDelco replacement pump (should be an EP386). Once the tank it out, use a brass drift to undo the locking cam ring and the entire sender comes out then there is a hose clamp that holds the a little section of fuel line to the outlet of the pump, Remove the clamp, remove the old "sock" filter, remove the rubber isolator under the pump and replace the pump, filter, isolator and you may need to replace the little section of fuel line...
Yeah, you only need the entire sender if the send protion is not working right...
Chris