As to the task itself self, finding a working logic board will be hard as most failed from [https://en.wikipedia.org/wiki/Capacitor_plague|Capacitor Plague] as the small electrolytic caps dielectric often corroding out the cap.
Also keep in mind this system almost needs a few disassembly to get the logic board out and the connectors often break just from age.
Here’s the guide we have [guide|257]