You asked 20 questions in your post. You probably won't get the kinds of answers you want by asking for everything. Many of your questions are discussed daily in the forums and good starting points are the FAQs in the Newbie section.
Also, check the "show off your project forum" and search on "Tahoe". There were seven projects in there that mentioned a Tahoe.
It will take a lot of planning to successfully put a computer in your truck. That is because each installation is customized for your car, budget, and needs. You should expect to read an awful lot before being ready to install. In the meantime, I often point new members to the following location to assist in planning their systems: http://www.carnetix.com/DecisionTree/DecisionTree.htm