Have you looked into touch screens? having full control of all you software w/o a mouse or keyboard rules
I got a great one of ebay for $50 (I lucked out on that one) w/the control card, ist's a bit big to go into a dash, 9.5" screen but I have seen smaller screens, it just takes time to look and wait for one to come along
.If you have more money than patience earthlcd.com has some nice expensive models,
If you really want buttons and a screen in a 2DIN space look for a wide 16:9 screen and you can fab a face plate that will leave space for lots of buttons along the bottom