Quoted from KDPinball:but the there are a few pins on U42 and the resistor next to it that are corroded.
That is a capacitor and not a resistor.
Quoted from KDPinball:What's my next move?
I would carefully cut off the battery holder and inspect underneath for more damage.
Hard to say but there maybe something on U-52 too. Post a pic after you remove the battery holder.