Welcome to the world of EM Pinball repair (and restoration - which will naturally follow). To make your journey easier -- start here -- http://www.pinrepair.com/
scroll down to this section:
1930s to 1978 EM (Electro-Mechanical) Pinball Repair Guide
Guide for fixing electro-mechanical coin operated games
of all types including repairing pinballs, bowlers, pitch & bats, etc.
made before 1978.
This will tell you everything you need to know about how they work and how to troubleshoot and how to repair. Take the time to read through it and being a fixit guy and an engineer you will pick up on it quickly. This info plus the vast knowledge of all the EM folks on Pinside will get you through anything