Hi, I just purchased 2001 QX4 in January. The car was in decent condition but I performed the maintenance just for peach of mind. Here's some items that needed work on mine:
-Oil Cooler Leak - Needs a new ring seal. <12 dollar part that you can find on amazon and a 15 minute job.
-Replace all differential fluids and transfer case fluid
-New coolant, air filter, & oil change obv
-Replace trailing arm upper/lower - pretty easy job
-Cam position sensors were throwing a code - replaced both 160 dollars and 10 minute job
-Rear Glass Struts - lot of people don't notice that this, 30 bucks on amazon 5 minute job
-Replace the serpentine belts - bought the 2001 pathfinder specifically to avoid timing belt issues
-New coils in the rear, struts in the front, and shocks in rear when lift was put in
-Replaced brake pads in front, new drums and shoes in rear, regreased the wheel bearings and then added warn hubs
-Replaced interior lights with LEDs both roof lights and lights behind center console & clock
-Added refrigerant
-replaced fuel filter - cheap part and easy job as its an in-line fuel filter so you don't need to remove the fuel pump at all
-Replaced the spare and got new AT tires and wheels all around
-
Future Plans
-Oil Leak from Valve Cover Gasket - plan to fix in the future but advisable to replace Knock Sensor, PCV valve, IACV gasket while you're at it
-Coolant hoses and water pump - keeping spares and waiting until failure
-Adding a hitch for a tow point
-Rocksliders
-Probably upgrade from 31inch tires to 32
Hope this is helpful.