I spent 11 hours on this 5162 today. Still doesn't POST but at least it's improved cosmetically? It's all buttoned back up for now. I need to do some more research/studying before I open it back up to continue troubleshooting.
That manky IBM 5162 wasn't bad at all inside. No signs of water intrusion and the motherboard looks clean except for these tiny spots of corrosion. I've cleaned them up but the board still appears dead.