If I were you I would go over to Maptools and download one of Torstan's free sets. It should give you an idea of what you want to think about. If I remember rightly there is also a free set from Devin Night. Then from there you may have more or less questions

I don't know anything about .cmpgn files though so I'm in the same boat as you on that one. I need to find out as well I guess.