I concur with Todd.

If the goal is move it along, then the cheapest/fastest route is to offer it 'as-is'; if you got it for a good deal, you can pass that along and save your time for the next project (perhaps a single-player). Or offer it as a trade for a single-player.

But if you really want to bring it back to life, the happy medium is to try to get it operational first (i.e., start, reset, advance through 3 or 5 balls, go to game over). The downside with this approach is that you'll likely encounter multiple problems all at once, which makes it confusing and challenging to triage and work through. So the hope is to first inspect all the moving parts to make sure they physically operate (steppers, solenoids, etc.), make sure there are no loose wires, check the fuses for correct size, no mangled switches, and manually place everything in the reset position (zero out all score reels, reset the relay bank, unlatch the interlock switches, reset the steppers, and so on). Then you can further assess what may be required after firing it up.

Personally, my order is: cabinet, score motor board, backbox, depop playfield topside, do playfield underside, do playfield topside, power on for first time. But everything gets a complete tear down/rebuild as I go, which isn't really the time commitment you're going to want to make yet.

Transformers hardly ever fail, and even so, can be replaced without needing to part out an entire game.