You certainly jumped in headfirst! that should be an awesome bike.
don't forget, you have to post pics when you get it!
You'll need pedals first, so do some research on what you kind of pedals will suit your usage. If you go clipless, most people put MTB pedals on their cyclocross bikes
Accessories: get the Giant RideSense speed/cadence sensors, with a bike computer to track your rides (GPS one if you want to track your rides in detail). Other than that, you'll want shoes, helmet, bicycle shorts. The bike store should be able to guide you on that.