Tommy,
I most definitely agree with Kent's suggestion. Bayeux is a great home base for touring that area, and you could also see the famous Bayeux Tapestry while there. It's a wonderful small town, easy to get around and has some great restaurants!
The BattleBus tours are awesome! Check their website for complete information and prices. The tours depart from the parking lot near the Churchill Hotel and last a full day (lunch not included). The Guides are incredibly knowledgeable and I felt I learned a lot more and covered many more locations than I would have on my own.
I took the American highlights tour one day (St. Mere Eglise was really interesting!), and the Canadian highlights tour the next day. Some of the material was a bit "unpleasant" (standing in the garden of L'Abbaye D'Ardenne was an especially sombre experience, as were the details of some of the battles that took place around Authie and other small villages). I felt I had a much greater understanding and appreciation of the D-Day events after taking the BattleBus tours.
Getting to Bayeux from Paris was an easy 2-hour or so train ride from Gare St. Lazare (one of the Paris rail stations). If you feel you want to rent a car to see Mt. St. Michel (or whatever), you could always get a one-day rental in Bayeux (ask your hotel or travel agent to arrange it, as the rental agency I used didn't speak much English).
As you'll be travelling in "peak" season, you might want to get some hotel reservations and other details sorted very soon. It would also be a good idea to send a note to BattleBus, as the tours can book up very quickly!
Good luck and happy travels!