There is a fair bit of work done since Maya 5.
In terms of user process nParticles are similar to regular particles but with a lot of useful added stuff. Jump directly into using them...as far as I know any documentation you have about the old particle system will still apply to nParticles.
You also have nucleus nodes which allow you to make some nifty global adjustments shared between your particle shapes. You can have multiple nucleus nodes or just one for several nParticleShapes. The nucleus is worth some investigation, it's like an environment control.
There are a some demo scenes with notations in the visor, really worth a look.
Duncan's blog (on this site) has a lot of good stuff on it, lots of example files.
Also if you get comfortable, have a look at Peter Shipkov's free Soup plugin. It is full of particle controlling magic.
http://www.soup-dev.com/I've not tried Sparta but it looks incredible:
http://www.cgchannel.com/2012/09/meet-sparta-its-like-zbrush-but-for-particles/Do a google for "pinp my pipeline". Two of the videos are presented by Duncan Brinsmead, in the second one he runs through a lot of different techniques for particles and fluids.
Good luck,
Ryan