I need information on fitting a second hand fuel.

Do not waste your time with a second hand pump, you are far better of with a new one, remove battery, un do fuel lines and plugs at pump, undo the ring of bolts and lift pump and housing forward, if tank part full you will start loosing fuel so be careful to catch it, now you have to feel in side the pump with your fingers and undo the fuel return line, this is the hard bit, with that removed carefully lift the pump and sender out of the tank making sure that the sender float is not damaged, remove pump from sender housing, unclip wire and feed line first, re fit in reverse order, getting the pump in and seated correctly is a difficult as is re fitting the return line.