Please help:

I have a 96 Discovery, 4.0, AT, NAS.

While traveling down the highway at 25 MPH I heard and unsettling noise from
the rear. I immediately hit the brakes and threw the car in neutral as the
diff made a LOUD clunk. I put the car back in drive and heard some grinding.
Not good.

Actuated the diff lock and limped home. I did not hear any more grinding for
the rest of the ride.

I was able to get the diff off the car and low an behold the planetary gears
took a crap. After a complete inspection...

The ring appears to be in good shape, no missing or mangled teeth. The
pinion on the other hand and 5 chipped teeth, not too bad just a little at
the top where it makes contact on the inside of the ring. Again... the ring
is in good shape no teeth missing.

Questions:

Should I replace the pinion? I can see if it was worse, but... I don't want
to be in this predicament later.

Locker, LSD or stock? I am a moderate off roader and it only makes sense to
upgrade to a locker at this point. I am to understand that the Detroit
locker is far stronger than stock. I have a LSD in the front already with no
problems.

Any suggestions?

Thanks.