Finally making some progress again! I got my new wheel installed, & initial around-town results suggest the vibration is gone. I plan to take it for a highway test soon. I also dropped it off with the mechanic this morning. Over the weekend, I crawled underneath to snap some "before" photos. I also snapped some of the rear, exterior frame area around the gas tank. The mechanic will be cleaning up & undercoating the areas I can't get to, & I'll tackle the rest once I get it home. Once that's done, I can reinstall the roll pan.
Some "before" pics here, along with all the new parts:
https://flic.kr/s/aHskuDoSGL