Hi JimmyPardon my ignorance, and I'm not as versed as others here, but you had no issues with the gearbox, and the only reason you took it out was because you wanted to change the sprocket.
Why not just fit the new sprocket and ride the thing. If you start developing issues in the future, you can revisit it with a little knowledge that there is some wear, but as you discovered it is easy enough to pull the clutch and gearbox.
It would be great to have a proper explanation from the experts as to what we're looking at in the photos.
I'm going to run it as is until I find new gears at a reasonable price. There must be loads of bikes running around with tired gearboxes out there.
I just don't want mine to be the one that seizes up on a ride!