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 online.
Just enter your vehicle information and then click the link on the left that says "repair info"
FYI.. the only .pdf version for the 3rd gen Maxima is the 1994 model. you can use the section for the GXE which has the VG30E stuff in it for the early models. 92-94 models are all identical and the manual is fine there.
the only problems you may have is if you have an 89-91 5 speed model, and the transmission for that one isn't shown. In that case, you can likely find the info you need on autozone's website, or other places online.