CM Newbie Help

[Major BS]

Howdy Gents (and Ladies?):

I've been on the CS ladder comfortably for a while. After hearing many good folks rave about CM, I decided to broaden my horizons as it were and tracked down some CM discs (Beyond Overlord SE, BB SE, and something called the "English Edition" of CM3). If you all could be so kind, I have a couple of questions before I let you all wail on me once I get on the ladder:

1. What versions of these games are most commonly used on the CM ladder?

2. What updates are necessary to get to the versions mentioned in Q1, and where do I get them?

3. I've noticed a ton of mods here and there on the net. What mods are most helpful to learning/playing and/or most commonly used among Blitz CM ladder gamers?

Thanks in advance for all your help. Once I've slogged through the rulebook and updated accordingly, I hope to get on the ladder as quickly as possible!

Thanks again,
Brad