Hi, have had my old girl in the garage and have been told i need a new pump as the stop soleniods had it

. Paul (chap who looked at her) says the pumps are coded and i need one with a matching code ? ......., can someone tell me whats that about ? and, does anyone know if the pump was fitted to other make/models so i can expand my search as at the mo i seem to be drawing a blank
Also, can anyone tell me if changing it is as big a pain as it looks ? ........, as capable as i am it looks like one of those jobs i'd be better off getting done for me ? ;) lol