You have two choices to MSM:
The E05 to the NW, then the E46 to the E401. That will take about four hours, depending on how well you do getting out of Paris and what you find after Avranches. This is the quickest route, but not very exciting unless you pause at Rouen or Honfleur.
The other way is SW out of the city toward Chartres and Le Mans and then north. The last twenty miles on this route can be a bummer and can easily take you five hours. The advantage is that you can stop in Chartres for the cathedral.
For perspective, you can see all you want to see at MSN in two hours and it's better from dusk onward.
Tossing Beaune into the mix adds possibilities. A straight shot from Caen is about five hours (but the Paris ring road could slow you down a bit). If I were going to do this, I'd use the Chartres route above to MSN and then the Rouen route heading to Beaune (it wouldn't add but about a half hour driving time). A car is handy for Beaune and makes it easy to slip into Dijon (Beaune can get old fast).
Get a car as close to your hotel as is convenient. You can't, by simple geography, be more than a couple turns and fifteen minutes from the Peripherique ring road which will put you well on your way.