leaky front diff gone bad?

I posted awhile ago about my leaky front differential on my '98 blazer. just now took it to a mechanic who is a friend of a friend. he jacked it up, and you could here a ticking noise when you spin the driver side tire coming from the differential. but ONLY on that side. He said i went dry and wrecked something inside the diff. He suggested I look for a used differential. There is noise while driving.  To me it sounded like it was coming from the bearing right where the axle comes out. what should I do? It seems to me that if I needed a whole new differential that you would hear noises on both sides. Am I wrong?

Its the outer bearing. It might cost about $30-$40 in parts. If it were me I would change both sides (bearings and seals).