Trackpad installation shortcut was great
The trackpad seemed to have become possessed. It began running the computer the way it wanted to - deleting files, opening programs - whatever struck its fancy.
I chose to go with the shortcut and leave the existing cable intact so that I didn't have to take out the motherboard. The previous hint was a great help. Just using the spudger to gently pry the ribbon cable off the trackpad worked wonderfully. Getting the cable back into place just needed gentle nudging.
Thanks SO much to ifixit for this website. I'm much more confident about making repairs - certainly replacing parts is a breeze because of them.