1. The wiki has some sizes listed in terms of cargo holds required in the commercial shipping tutorial. A terraforming installation requires 25 cargo holds to move in one piece. hxxp: aurorawiki. pentarch. org/index. php?title=Commercial_Shipping
2. Yes, you'll need to start moving colonists there before the terraforming actually begins. If you hit f2 and look at the summary tab for mars, it'll tell you how many colonists are needed to operate your terraforming installations on the left side.
3. I like to think that's exactly what they're doing with the infrastructure that you send them.