www.ricksteves.com. Also go to the book store and get a couple Rick Steve's books that are specific to the cities you want to visit. My wife's brother used to work for Rick as a tour guide all around Europe and we find his guides to be the best when traveling there.
We did two weeks in Germany, Austria and Cech Rep last October and had a blast. What worked best for us was to book airfare for our trip there and back and a hotel for the first couple nights in the first city. From there we made travel plans once we arrived based on what we felt like. Trains go everywhere and are ususally easy to get tickets for. You can book hotels at a local internet cafe. Europe really is easy to travel around so it makes it very easy to plan as you go.
Have fun and don't stress the up front planning.