I'd go with a new board.

Unless you can do the repairs yourself, you'll likely be money ahead.

LTG : )

That was my thinking. And what about down the road even after repairs, in which you'll discover more damage.

LTG : )

I might spend a couple hours on that to do some cleanup and replace a few components just far enough to see if it will boot and if the switch matrix works.

If it boots and the switch matrix works, then it might be usable with some more work. If it won't boot or if the switch matrix is unresponsive, then there's not really much point to digging into it further since there are some good aftermarket MPUs available.

I like to go with pascal's MPU since it adds a number of nice features (like attract mode light shows, increased bonus count down speed, ball save, plus a few other bells & whistles).

The pictures don't show it, but have you looked at the backside of the board? There may be damage as well along the edges where the connectors fit. Sometimes very bad.

That does look pretty crusty. If you have free time give it a go cleaning it up. I wouldn't mess with looking for a working original board to put in if you fail, just get replacement boards of your favorite flavor (pascal, niwumpf, lisy) and replace.

Make sure you update the driver board with protection diodes:
https://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_1#Driver_Board_Issues

If you decide to replace the whole set of boards with the pascal x4 don't bother with the power supply or driver boards.

I agree. With the original Gottlieb cpu board, you never know when one or more of the spider chips will suddenly die on you.

Or do it yourself and try a LISY1 https://lisy.dev/lisy1.html

User 'lint' has just ordered 5 PCBs and offer some spare ones

https://pinside.com/pinball/forum/topic/diy-lisy-a-replacement-mpu-for-gottlieb-bally-amp-stern#post-5779615

I've had good results getting these boards going as long as the corrosion
isn't too extensive. Have yet to buy one of the replacement boards.
If you've got some skills working on boards give it a shot. It helps
to have bench supplies, a scope and function generator so you can
do all of the work on the bench.
Steve

Buy a ni wumph. Great support, skill shot and many other options on newest version.

And, ni wumpf is an American owned company

Honestly; I was looking for a train wreck... but I'm hard pressed to see much corrosion.
I've seen much worse be functional.

If you have the money; and a lack of time... buying a replacement board is a fair option.
I however, tend to appreciate that the original boards are still in the machine.