Just did a tour this summer. American cemetery by Omaha is a key place to see. Airborne museum is one of the best museums. If you only have time for one, it is the most complete (in Sainte Mere L’Eglise). I also recommend seeing Pointe du Hoc. Key story of the landings and impressive bomb holes. We also saw Pegasus bridge where it all started with the British landing in gliders. Nice little museum and amazing story. Sword and Juno beaches near too.