Thank you Pat.
I still have a few good length dimensional lumber from the original wall - so that would be good for the top plate, and I think I have several in about 8' lengths which would work for posts.
It did indeed rain all day today - this is what the back of my yard looks like whenever we have heavy rain. It's a very high water table, there is a stream that runs around the outside of the property between me and my neighbor, and the soil only goes down maybe 2 ft or less before it becomes clay
For perspective, this is the view from the house (different day) right-hand side (West) is where it pools..
Even with that, the back of the garage did not get very wet or have any accumulation to speak of. So, I think I can just backfill that area with gravel.
Since I couldn't work outside, I just did some more cleanup inside. Added sheathing to the inside of the garage doors, as those were pretty darn drafty and also a little wonky.
While I was at it I also put some primer on the new shelves and upper sheathing
Rain is supposed to stop later today, so hopefully tomorrow I can start with the jacking and replacing of the sill sections.