When I picked up my plane the pump was dead and I insisted on a new one for the trip cross country. Ordered one overnighted from Cal to FL and watched the mech. install. He used a flat blade screwdriver and light hammer to loosen the nut and re-tighten it. He was very careful and tapped lightly on the lobes as needed to loosen and reinstall. Still doing well after 507 hours.
Would love to pull it and clean it so it goes another 500 hours, as I hear they can if one routinely cleans them, but it's a process....
Good luck.