Headrest --- Pull them straight UP as I recall. When you fold down the seat.....I think there are holes in the back that you can stick the headrest into......I sure hope I'm not making this up. You may want to wait for one of the wagonmasters to chime in here.
If you need a front windshield, there is one in the boneyard here. And I have some SLS parts......
Oh, I have some blue seats, too.
Of course, if you find the car is too much work, please let me know. I'm still searching for my FIRST wagon.