Ok, first off, go get a Factory Service Manual here:
http://www.nicoclub.com/FSM/
Then, go here:
http://www.courtesyparts.com
Compare the 04 pathfinder (same as a QX4) rack and pump parts to your 01. Mu guess would be that the part numbers are the same or near identical. THey'll have spreads you can compare the parts. That should help you with the what if's and what not's.
Beyond that, just make sure you've got a spare vehicle for a parts runner and you're set.