You need to read some.
Here's a link to a beginner's FAQ that will help you out with every question you have, with the possible exception of the radio question.
The general consensus is that the radio solutions for PC don't work well in a car. Some members here developed a solution for AM/FM radio in teh vehicle that's superior to any other commercial offerings, but it's new and has limited software support as of now.
Search the forums for HQCT Radio and you'll be able to read all about it.
Welcome to our hobby, and hopefully you'll still love carputers once you start building one....