Hello and thank you for your ambition!
The easiest way to see what files need translating is to download the Brazilian translation (found on this forum) and have a look at the files packed in there. Generally speaking, most of the text files are in the English, Campaign and Data folders. Yet there are some tricks needed to access protected files. It should be pretty intuitive once you look at the other translated pack, but if you have any problems or want me to get into details, let me know.
We can also continue this discussion on email if you prefer, I am quicker to respond there.
EDIT: Looks like the download link expired, but you can still see the changelog on the Brazilian topic which shows exactly what you wanted: the directory paths of the translatable files.