Input shaft - life left or replace?

That's high gear.
If it were for my own vehicle, I'd likely sharpen the points and try it, prob be okay. Replacement is fairly easy .
I seldom speed/power shift into high gear .
jmo
You might get away with it... But teeth like that not only effect the shift into high gear but also can cause it to pop out of gear.... It's available, in the past availability was always a problem... If you are strapped for cash patch it, if you aren't a starving car guy replace it...