My first bit of advice would be to stay away form the new version (3.0) until they fix the bugs. On paper it's fantasic, but we have recently moved back to the previous 2.x versions for stability.
If you already have data, spend some time creating server templates that are realistic. Becarful on HT loading, and network/disk thresholds.
They start playing and see if the modelling "looks right" to you. Once you have confidence with your server templates you can model away!
Dave