a noob map modder question

[Kojusoki]

Hi guys
For a long time I have been thinking about creating my own map, an ancient europe. I was searching the forum and there are a lot of tutorials, hints etc but for nation modding/creating - almost nothing about map making. Is it so easy or so sophisticated?

So far, I understand that it works this way:
-I have a jpg file (like map of europe)
-I convert it to a tga format file (why!?)
-I place borders, extra graphics etc, just for HUMANs (I mean Dominions software doesnt care about borders etc)
- I place A SINGLE PIXEL which is completly white (RGB 255,255,255) in each province. (how do I do this?)
Question: how a computer knows which pixel is which and in which province?
How do I number the provinces? According to raws? Columns?
-I create a txt file, in which I use command like neighbours etc, so the Ai will now where are the connections
-I change this file from txt extension to .map (why?)
-I am removing bugs

The "adventure" map:
when the previous one is working, I am adding special sites, starting positions etc

So it seems pretty easy - question is how to make those extra white pixels, how to give them numbers etc