I took everything apart yesterday. If you want more detail, check out my Instagram account (@valveandpiston) where I documented the process.
It looks like the culprit was the lower shaft bearing. When I took the bushing/bearing off, it felt like clay was lodged in the needle bearings - very gunked up. After cleaning the bearing with brake parts cleaner and applying some silicone lubricant, I felt that it could be salvaged. I also cleaned the U-joint, but did not apply any lubricant. The U-joint was very tight. I took it for a test drive and didn't feel any symptoms. See below for before/after:
Before
After
And a picture of the steering shaft, which I cleaned up as well.
However, I am still a little worried that this was not the entire issue and it could be the steering lock mechanism...