The skull that it includes is "Grunt Funeral." The one you're thinking of is "Grunt Birthday Party," which is already in the game.
The reasons that I wish we got a special edition here (I'm in Canada) is for the Steelbook case and the Master Chief statue...
Your assumtion is incorrect... Halo 3 came before Wars (in release order, not chronologically)... There. You learned something.
I learned to never, NEVER, NEVER let the AI drive. Ever.