It is more basic than a lot of people think. The computer tells you where the problem is usually for the most part. Most of this crazy gouging for basic car stuff is just the companies strategically placing things in cars so they are hard to get to for the average person to boost their profits. Many of those expensive services and part replacements could be done after watching a youtube clip explaining it. Also they gouge on parts - if the part is available at an auto part store it will be way cheaper then the dealer/shop is for the part usually. People just like to get conned it seems.