As a starting point, start going on Youtube to find videos on how to use a multimeter if you don't already know how. Download the FSM on a computer, not on your phone. You may want to print out the BE section. It has some excellent breakdowns of the circuits. from there, you get to dig in and see what the hell the IPO (idiot previous owner) did. We can coach you through a lot. Also download the wiring diagram for your year Z from AtlanticZ. Philip did a great job cataloging the different diagrams.
Be patient. If we tell you to do things a certain way, it's for safety, efficiency, effectiveness, or some combination of those. With patience you will gain knowledge, and you can enjoy your car for a long time.