I would drive the route first, then I too endorse with the weekend test ride. Big help. You'll be surprised how much elevation change there really is on your ride.
Also, when you are driving the route, think about how much room there is for your car and a cyclist, where are the tight spots? where might visibility be low? where might you, the cyclist, have to avoid the door zone? Where might you need to take the lane? How will you handle left turns and large intersections?
Try some alternates when you have plenty of time. I'm favoring wide roads over slow ones in my route.