I doubt that you're going to have to replace either, barring a failure not in the sear itself, but in the hinge that attaches the trigger rod to the sear. In my eyes, that's the weakest part of a 'Mag, next to o-rings. But even so, it's likely that you'll never have to replace it.
I'm really not good at writing signatures. I mean, what is it that you're really trying to do? Write something that somebody's actually going to remember, or even read? Yeah right! Nobody ever actually reads these things.