www.phatg20.net has the Nissan service manuals in .pdf form. Definitely worth registering on their site. Keep in mind these are "grey market" manuals, similar to mp3 and movies downloaded off the net. If you're not cool with that kinda stuff, then purchase a print version from your local dealer or find a used one on ebay.
You can also log onto www.autozone.com and get most of the information you need. it's basically a Chilton's manual in .pdf form.
Just enter your vehicle information and then click the link on the left that says "repair info."