1: Get a 24-70 to go with the 70-200. You will also want a macro lens for the detail photos.
2: Learn how to bounce flash, use a diffuser, as well as gelling and balancing flash with ambient. Strobist is a good resource, and there are lots of vids on YouTube to help.
3: Make sure you are ready for doing one time events. There are no re-do's. You have to be confident that you can get the shot in any lighting while under a lot of stress. Second shooting for an established wedding photographers is probably the best advice I can give though. There you will learn how a wedding works and the flow of events as well as what things are needed and what are not.
4: That's up to you. If you don't know what others in your region are charging you need to do more research.