That's a great looking bike! Congrats. Sounds like you did right by your LBS.
You need a helmet. All helmets sold need to be certified, so any helmet will do.
Go ride. You'll figure out what you need to add as you go.
Do you think you will need to fix a flat on the road? If yes, you should have a spare tube, patch kit, tire levers, latex/nitrile gloves and a frame pump. Why a spare tube and a patch kit you ask? It's easier to swap the tube, but if you get a second flat, you'll have to do a patch job on the road. I live alone, so calling for a ride isn't always going to work for me.