2001 Maxima AE bad transmission

[aemaxin]

I have a standard shift AE Maxima with transmission problems.... From what I have seen, the transmission in it has the locking differential but I could be wrong. What is the big difference between the locking and non-locking differential? Is it a big plus for me to have it? Can I mate a non-locking with my car? Will the '02-'03 6spd mate to the 3.0 in the '01? Where can I find parts for the original, they are very expensive and hard to find where I am........?

Thanks