How Do You Break Down a Top Case?

Need to replace the trackpad on a PB G4 15"/A1106; doesn't drag and drop properly. I'd like to purchase just the top case trackpad assembly (without the keyboard)--cheaper that way--and then fit that over my existing keyboard after I disassemble it.

But I've never taken a keyboard out of a top case, so I'm a little nervous about attempting it and I can't find any instructional videos out there on how to do it.

Anybody done it before?