Papa and I finally had the time to do this recently.
The inards were simpler than I thought it'd be. Just a main circuit board in the middle, a smaller one at top for the volume and tone controls, and the keyboard itself. There was some gooey thing where the keys contacts the board which was causing the stickiness. It probably is spilled coffee or hot chocolate. Nothing that rubbing alcohol can't clean.
It's all cleaned now and the piano is working great. Now, just to find a spot where I can place this giant.
