Goatman—

Thank you for clarifying things for me; I’m going to have wait until next week to get back to this project (I’m swamped with work—when is this not the case?), but I will post back to update progress. In the meantime, I’ll get the multimeter out of the box and familiarize myself with it.
I think another explanation besides (or in addition) dislodging or breaking a vital connector or wire, could be that water caused some electrical damage, for when I lifted the carpet today on the other side from where we had been working on the taillight, I found water in the wheel well area. Obviously, this is another problem that needs to be addressed as well.
Thanks again for the help.

Until next time,

PVC