Damn that looks nice. You got yourself at least one blown fuse. Rule 1 replace with the correct fuse for that fuse holder. Don't go by what was in there. Go by the writing next to fuse. However, expect a new fuse will blow again. Don't start "filing" contacts. I used to use strips of brown shopping bag paper and 90 per cent alcohol to get the carbon out of the contacts. Hopefully you have schematic or can get one.
Take your time, I know it's hard because you want to play it. Going at it though without full knowledge can make things worse. And, keep the WD-40 as far away as possible.
Again that looks like a peach of a game. Congrats!
Try Pinball Resource for parts, however they are Gottlieb leaning.

Get some close up shots...under the play field and inside cabinet.

As mentioned once the short is found, a fuse goes back in. Another fuse tool I find helpful in some circumstances is a current limiter, which is a light bulb of the same voltage of the circuit you are testing and replaces the fuse as an indicator. If there is a short, it will be bright. If it's normal, it won't light at all or will be dim. I learned this trick building guitar tube amps. After the many hours of building a tube amp, the first test, the 120v hot goes through a 100w light bulb. If all is good, bulb will glow brightly for a second then dim. If the amp is mis-wired, the bulb will glow brightly period. But it will not destroy the amp, it will indicate that you have a problem.
You said your score reel was broken, picture indicates the singles digit is sitting at 1. If that's the case possibly the cam motor won't stop because it can't "see" 0.