When a mechanic identifies grinding noise in front wheel when turning right as worn bearings, is the only thing that is needed a replacement a front differential bearing?

If a bearing is bad you must replace it. I would first suspect the hub bearings, not the differential bearings but your mechanic has first hand knowledge, I can only speculate based on what you posted.

when driving and you turn left does the noise lessen and get louder as you turn to the right if so replace your rf wheel bearing

Thanks for the answers. Found the correct hub bearings and ordered them up for both the left and right.