Thats a great idea.
I myself have been struggling with the same thing. I got the realtime ecu, thinking it would be super easy, but I am finding myself not able to quench my thirst for knowledge about tuning these things.
The neat thing is with the realtime you can also get experience tuning using basic ecu code, that is not only pretty universal for the most part, but allows you to understand how your ecu works.
That said, the realtime is a GREAT thing to have. Even if you cannot tune worth crap, it allows you to instantly load any program onto it if someone already has a tune available for your setup. Also, with free programs, you can hook your computer up and monitor live information about the ecu. Really handy!
A link you might not have found yet: (props to hypro123)
http://www.sr20forum.com/sr20de-technical-corner/25488-ecu-tuning-per-%22down-under%22-part-1-a.html
There is some other information over on sr20forum. One thing that was suggested was to read the entire ecu database over there, its allot to read but I have started to do that because the information is scattered and its bits and pieces.
There are some links to other write-up's on Nissan Ecu's that are also really helpful, so if you can find those ( I tried for a good 30min and cannot find em, sorry) it will get you off to a much better start then I have had.
Gl, tell me if you find anything awesome.
Dudeman