Congratulations on the new bike!

Dura Ace is Shimano's top end componentry. It is lighter than Ultegra and has nicer finishes. Ultegra performs beautifully and costs less. If you aren't a racer, you probably won't notice the weight.

As for the gear ranges, one of the mechanics who post here could probably answer better than I. I'm sure your Local Bike Shop could supply the answers too.