I signed up too for the TDH 70 mile route. I agree that the route looks boring as heck - I've never been on a sponsored ride like this that's an out and back. Oh well, if nothing else, it should at least be well policed, right, since Bill White rides in it???
Cycledorchy, I'm a noob just like you, training for my first MS150 this year. I don't have much wisdom to offer yet, other than the fact that I've done quite a few of the recommended rides in the last 2 months for the MS150. Most of them have been pretty well supported. I can tell you that I've found that there's not much need for you to bring a lot of extra food/drink on the actual ride. All these rides have reasonably placed rest stops with at the bare minimum, bananas, oranges, water and gatorade. Even the worst planned rides have had this. The better ones obviously have more stuff.
If you pack anything extra, I'd just say to make sure you have a patch kit with some tire levers, at least one extra tube and some way to inflate that tube, and be familiar with how your inflation device functions. Please don't ask me how I know this.... Also, if you've never changed a tube/tire, a recommended ride like this is NOT the place to learn. Others may disagree, but I learned in my garage on a rainy day how to change road bike tires and tubes when I bought new tires and tubes and Velox tape for my rims. Fortunately, I've been changing MTB tires and tubes since I was a teen, but you'd be surprised how many of my buddies that got me INTO road cycling tell me they have no idea how to change a tire. I keep offering to show them outside of our rides, and they keep declining. I just know someday I'll end up teaching them on the side of the road....
Good luck, and remember - just have fun with it. Go at your own pace and be sure to always say 'On your left' when you pass and I always say 'Thanks' to those folks passing me who call it out. Just a courtesy thing. NEVER pass folks on their right. I was on the Spring Breakaway ride last weekend with my buddy, and some jerk tried to pass a couple in front of us on the right. He ran out of road and went into the gravel, and when he tried to hop back up on the blacktop he almost wiped out and took about 5 people with him. Very disrespectful....
Let the Lance 'Wanna Be's' bonk out at 30 miles because they think they're on the Tour de France....