Editing .DAT files. Where to begin?

[Silent Howler]

I did some browsing and digging around, but surprisingly I didn't find anything as straight forward as I was hoping for, so I'll try posting a topic of my own.

I am a bit inexperienced when it comes to editing .dat files (I have only done it once for this one internet game) and haven't messed around with FFXI yet. Anyway, I suppose I'm looking for a walkthrough. Where to open up FFXI .dat files, how to location the specific file you want to edit, and probably any other important notes I should know.

Also, I downloaded one set of files (found here) but can't seem to figure out how to view what the files actually look like, except for the window boxes.

[Akashimo]

Go this way
Ye Olde Grumpy Rarab's Modding Guide

[Dracovivi]

Various other guides, relating to a almost all methods of modding can be found here