Actually, according to Strava it IS fairly hilly - approximately 2,000 m worth of climbing. That is quite a lot for a novice cyclist to do in about 130 km.
Just build up to it steadily, DJ. I'd want to be comfortable doing (say) a 100 km ride with 1,500 - 1,600 m of climbing a week or two before the event. If so, the excitement of the day should get you through it in good shape.
Have fun!