Based on the way you rode on Sunday's ride you will have no trouble completing the Clarksville Century. Between now and then I would recommend increasing your mileage each week by about 10%. I do not know what your longest ride has been but let's say 40 miles. If you increase that longest ride by 10% every week by mid-August you will be up to about 75 miles as your long ride. Try and ride 3-4 times a week with the other rides in the 20-25 mile range. This would give you a good base for the Clarksville Century and as you have said pacing yourself and eating and drinking on the ride properly then you won't have any problems completing the 100 miler.
As far as staying in a motel or driving up that's a toss-up. The ride's only a hour drive so sleeping in your own bed the night before might be more restful then a strange motel bed. I am sure several club members will be going up so car-pooling is a good possibility.
You might try doing the HOT-100 metric as a warm-up for the Clarksville century.
See you on the road
Cary

I have always driven up the morning of. You have to get up early, but the roads are empty. From the southern side of Murfreesboro it takes me just over an hour. This is a great first century. It was my first. The course keeps getting flatter and losing turns. I didn't know it could get any flatter, but they have managed to cut the climbing in half. Give it a shot. Good luck.