If this is your first EM pin, I would wait for a working one to turn up locally. They made plenty of Surf Champs and, at least in Europe, they’re not hard to find.
When it inevitably breaks down, that’s the time to gradually acquire EM repair skills.
I personally would not want to be facing a non-working game with multiple known issues and unknown history. I believe the Surf Champ cabinet is made of MDF, so if the garage was damp, it may have become structurally unsound.
Reading about EM repairs sounds easy in theory, but when you are faced with overhauling a major mech like the score motor or player unit it quickly gets scary.