Update: after cleaning and reassembling everything I now get:

- Green light after plugging in magsafe plug even though battery is dead.

- Holding down the power button for 5 seconds turns the magsafe light red and the battery charges.

- No other response to the power button - no POST, no noise, no power light - just dead.

- Disconnecting and reconnecting the magsafe always requires a 5-second power button press to initiate charging.

I'm guessing logic board is dead? :-/