I just took out the 5spd tranny in my 2k maxima because the diff. bearing is shot. The tranny has 41k miles on it. I'm pretty sure the synchros are fine, it shifted smooth as butter and I always rev-matched when shifting. When I drained the oil, there wasn't any shavings or debris.

Should I do a full rebuild or just have the diff. and input shaft bearings replaced?

 

IMO you are the only one who can answer that question. You have to disassemble the transmission and visually inspect the bearings, gears, snychros, etc.

I currently have mine disassembled and I only need to replace the two differential bearings. The input and main shaft bearings are fine.