Between Google, and YouTube, you should be able to teach yourself enough basics to keep your pins happy.
Get a meter, wire, battery, light bulb. Make a circuit so the bulb lights. Measure voltage on your simple circuit.
Then get a transistor, diode, learn to check them with a meter. So you see what good ones read like. Shorted or open ones will read different.
Don't worry about high tech or flaky stuff right now.
Just learn some basics and then apply them to your game.
If you never soldered before. Get an iron, solder, wire, and sit at your bench and learn to flow solder. Heat metal so solder flows onto and through it.
Same basics for most repairs in your game. Switch don't work, with your newly acquired skills with your meter, you can now check if switch is opening and closing, and if wires have continuity from switch to board in the head.
Then apply your detective skills - switch is dead -replace and gets wires and diode back in same spots. Good time to take pictures or notes to help you learn. Switch works, then follow the wire with your meter and find the break.
Apply same skills to lamps, and coils. Though your switches and lamps are usually part of a matrix, listed in your manual. This helps you know what wires go where.
GI is usually AC, measure AC voltage hot to common not to ground.
See, a half hour of practice and you know enough to do some basic repairs.
You can repair pinball machines. You just don't know it yet.
You get stuck, then post here. The pinball community is blessed with lots of help.
You'll gain in knowledge and skill and face your game with more confidence.
You'll do fine. Just don't over think things and stick to basics.