Experianced mechanic?

Hey I live in flagstaff, I'm looking for a mechanic who can replace the front differential in one truck and the rear in another....

does anyone know anyone in flagstaff that would be willing to do the job on the cheap? Figured this would be the best place to look.

or how hard is it to replace them myself?

just dont want to kill myself doing it...

or FUl( anything up.