So despite a long period of project stagnation, I have made some punctuated progress in the last 2 weeks. I finally got around to ordering the 7" display and touch screen overlay, and it seems to work (more or less) as expected. I only say more or less because the touch screen calibration is being a bit screwy, but I have a feeling that getting a fresh install of Raspbian may clear up the issue.
Now with almost all the pieces I need in place (minus a DC2DC Step Down Converter, and a DAC Audio Converter) I have to consider the real question of software. I've seen many implementations that seem to use Kodi or some other media center solution to drive their car computers, but I'm leaning towards a custom front end consisting of basic menu navigation with buttons and embedded elements (or convenient switching between non embedded windows.) I can't help but think my work may be cut out for me as these things scarcely ever end up as they work out on paper, but we shall see what we shall see.
I've posted some pictures of the touchscreen and the board that came along with it. The included board has several more video input ports that may come in handy if I decide to add reverse or dash cams. You can also see the touchscreen adapter and 5 button control module for the screen in the pictures. I hope to have more time in the near future to get some work done on this, so hopefully I can provide some more updates.