Tractor Repair: injector pump removal

Question
I was told my cav injector pump could be removed witout getting the whole thing out of time, is this so or should  be doing some lining up of things before I remove it.this is for a Hesston fiat 580 3 cylinder, I was told pump would only go on 1 way.

Answer
Well, it IS a pain to change it. BUT, if you carefully mark and reference the position of the pump, pull it STRAIGHT out without moving the gears, and reference the new pump EXACTLY as the old one was indexed, you won't have a problem. Be very very careful not to move anything.