Best wishes Wookie. Hope it all goes well.
The last time I seriously had an issue with a disk in the L4-L5 region the doc told me that when a spine gets to be older (he was being nice I think)...he told me that the disks get less resilient and the bones tend to grow things called spurs. The name reminded me of the kind cowboys use to giddy up their horses and the associated thoughts weren't good. As it turned out these "spurs" are extra bone growth that can sometimes affect your spinal function.
If the lump is a spur then a repair is pretty straightforward and routine. At least routine for them, not for you I'm sure. Best wishes on the outcome.
You mentioned when it rains it pours and I remembered your encounter with rain in your house at one point. Hope you got that all cleared up now.