Thanks for trying with the pictures!

Your machine looks like it has round thumb screws that hold the plastic mechanism on the wood frame. Try twisting those off and removing the entire mechanism.
There might be a few additional things that have to be removed or jockeyed to get the back off. But at least you can see how it works! And also make it easier to clean and get ball jams out.

There is a pachinko ball jam in the jackpot ball exit chute. I call the thing that lifts up to release the jackpot ball the "paperclip".
You need more pachinko balls to experiment with your machine or just try one ball at a time.
You also need to get the balls out of the payout mechanism in the middle of the machine, that is a round thing with a white lever piece.

I wouldn't worry about the wiring until the machine works but I know it's hard to resist. I like working on the lights the most myself!
See if you can find and identify the color of wires to each of the following: low reward light bulb, jackpot light bulb (looks like they are next to each other on your machine - what color wire goes to the center (+) of the bulb?) low reward tray switch, jackpot switch. I don't see a power block or a fuse on your machine, some fabrication will be required.

Not sure about those metal pieces, sometimes I have seen pieces like that at the top to protect wires and sometimes have seen pieces like that on the side to protect the main jackpot lever (yours is behind plastic - so not likely)