The ones you listed are folders that contain the files for that hud type. So, for instance, if you use the Player/Target hud type you want to open the player file inside the PlayerTarget folder. If you use the Health/Power hud then you would open the appropriate file inside the Health/Power folder.
The files are text format files so notepad is enough to make the changes. Just do a reload of the UI after you have made your change and you should *crosses fingers* see the difference.
If all else fails, take a look at this thread which is more in depth in its explanation.
http://www.wowinterface.com/forums/s...+aura+tooltips