I'm going to replace the fuel filter, which is the still the stock unit with almost 75,000 miles on the odo, and I'm going to change the air filter since it is due.

Got the parts from XterraParts.com

16546-00001 Nissan Air Filter - 2000 to 2004 Xterra V6 and SuperCharged 1 $8.74

16400-00001 Fuel Filter - 2000-2004 Xterra V6/SC 1 $12.08

So maybe someone else doesn't have to search all over the place and through threads with dead links to pictures, here is a link to a webpage with illustrated instructions on how to change the fuel filter .

ben