Got it done!

Mon problème

The trackpad apparently doesn't like water (even a drop of condensation from a glass), so it needed to be replaced. Soon. Don't like using a mouse anymore.....

Ma solution

The repair went great, the second time! After reassembly the first time, the MBP wouldn't power on, so I disassembled and reassembled again, making sure all the tiny, tiny cables were snug. After that, all was well!

Mon conseil

My only advice is just the standard stuff: make sure you have plenty of light, plenty of space to work (including room to lay out the screws next to you in the same pattern you removed them) and make sure the dogs can't get to your workspace to sniff around and rearrange the tiny parts!