So, did the dog get you on the return trip?
I'm impressed that you were able to tackle 50 miles so soon. If I were you, I wouldn't push the metric century right away--build up a good mileage base first. You are also discovering a lot of important lessons about biking. This forum should help speed up that process.
My wife has done two 50s and a 30 on her hybrid--and is seriously looking at road bikes now.