Basically type WW2 and D-day in an search engine. That is where you will get information. As for missions. Holding the bridge and taking the town that was what most of WW2 Europe was about. You could put in a Spe Op type mission or two. Go capture a german officer for information, free an allied spy, and sabtoge an airfield, factory, or research facility.
I would advise against making D-day a mission. If you search around you will see that many have tried, and I have not seen one that is any good.(there is new one that is suppose to be good coming out.) I would advise you to make that part of your intro. DC-3, flack and paratroopers at night, the landing craft, etc. A realistic D-day could be achieved with some skillful camera scripting. It would make sense to show the intial invasion because of your title "Invasion of Europe."
The missions are mostly going to be basic clones of BIS missions, with a WW2 flair. The main thing that will make people want to play is a good story. I can help with the story if you want. Good luck with your project.