Welcome Paulds.
What kind of bike are you going to use? I just looked at the event website, and I get the impression that it should be fairly flat and you can go at a steady pace if you wish.
As Paulus noted, if you are cycling any distance, (and you could easily be in the saddle for 4 hours for this one) it becomes more about fuel and fluids than about sheer physical effort. If you search through the 'Health, Fitness and Training' section here there is loads of good nutrition advice.