I have a 2003 Altima 2.5 S. I also am going to change my own oil, but will take everyones kind advice to read the owners manual, which Nissan was kind enough to give me, and in a handy, dandy zipper bag, of all things!!
Seriously, guys, the guy is just asking a question. Have the decency to just answer the question without being so damn critical. When I first started coming to this site when I had just a lowly '97 sentra GXE, I was impressed with the fact that my questions, no matter how stupid, were answered. Things are changing here, this is for sure.
Cubby-- You'd be about right on your 4.5 qt. guess.