The plan on the Cascades site looks good.
Just work your way up the mileage ladder and stay consistent, especially making sure you do back-to-back days of long rides. If you start your training plan now or early January, you should be just fine by the time the event comes around, and you can work your way up more gradually if needed. Also, make sure you take recovery weeks every 4 weeks or so (reduce your mileage alot for that week and make the rides easy).
While you're increasing your mileage, you'll also need to experiment and get comfortable with your on-bike hydration and nutrition -- you'll need to find a sports drink or two that work for you, as well as some "snacks" or food that you can tolerate and provide enough energy on the longer rides. You might try some of Hammer Nutrition's products like HEED, Perpetuem, Hammer Gel, and Hammer Whey (here's the link:
http://www.e-caps.com/ ). Even if you don't use their products, they have some good information on their site regarding hydration, nutrition, and recovery.
Good luck!!