There is no serviceable fuel filter; it is part of the fuel pump module inside the tank, so scratch that off your list. The VQ engines use coil-on-plugs, so there is no distributor nor spark plug wires. The spark plugs are NGK Laser Platinum and aren't due until 105,000 miles, so you're not due for plugs, yet. When you replace the plugs, #1 and #2 are a real pain. The service procedure calls for removing the intake plenum. It can be done without removing the plenum with the right tools and some patience. Stick with the same type NGK spark plugs that came in it! Avoid Bosch platinum and other brands. The air filter should be replaced every 30,000 miles. There is also a cabin air filter that is recommended every 15000 miles, but I usually change mine every 30000 miles. To access it, you need to lower the glove box down to access the door on the side of the heater blower case. There are two filters, side by side. You pull the first one straight out, then slide the other one over and pull straight out. That's about it as far as tune-ups, because the engine is computer controlled and there isn't much in the way of adjustment, especially without a scantool. Other services include replacing the coolant at 60000 miles and every 30000 miles, afterwards. I usually drain and fill the ATF every 30000 miles; Nissan Type "J" or "S" is the factory fill, which is the same as Castrol Multi-import ATF. I use Valvoline Maxlife ATF; do NOT use Dexron III/Mercon! I also service the transfer case every 60000 miles; you can use Nissan Type "D" ATF or Dexron III/Mercon, but I stick with the Valvoline Maxlife here, as well. I do the front and rear diffs every 60000 miles using Mobil 1 synthetic 75W90. If you do a lot of off-road or severe duty driving, you may want to change those fluids more frequently.
If you still have your original radiator, be aware of the issues concerning the radiators. The integral trans cooler has been prone to failure and can cause coolant to contaminate the ATF and destroy the trans. If you haven't addressed it already, there are two options. You can replace the radiator; I got an aftermarket for $92 shipped on Ebay, but it's made in China (haven't had any problems with it and it appeared to be well built). Canadian made Spectra Premium rads can be found for $160 online. Genuine Nissan rads go for $450 online/$550 retail. The other option is called the "bypass method." There is a factory installed auxiliary trans cooler in front of the AC condenser. Basically, the cooler in the radiator is bypassed and solely the auxiliary cooler is used to cool the ATF. So far, this method seems to work. Keep in mind the radiator's cooler also warms the fluid to keep it in proper range (around 175-200 degrees F.), so if you live in an area that sees very cold temps, the radiator replacement is a better option. For more info, there's tons of R51 info at the Pathfinder site: The Nissan Path :: The World Wide Nissan Pathfinder Owners Forum :: R51 / R50 / WD21 :: www.TheNissanPath.com