1. I have a 10.4" LCD touchscreen that I bought for $300. (search this forum to find the URL--it was on ebay and the guy has several left)It is friggin awesome. The way it works is that there is a panel in front of the actual screen that detects where your finger is. When you touch the screen, it basically moves the mouse to wherever your finger is and left-clicks.
2. Those units are terribly expensive, and I dont know if you can get them with a touchscreen
3. we need to know what kind of car you have before we can suggest to you where to put it