rear sight came off pretty easy. those headless screws had me worried. I used a small tap wrench, whose collet was just the right size to fit over the head. the screw for the collet of course doesn't fit between the ears, so I clamped the collet with vice grips...very tightly...then held all steady and gently turned...gently...keeping my eye on it for the slightest hint of slippage. Both screws came loose this way with no slipping. However, when I pulled the collet off it did scuff the bluing on the head - but both screws already had some scuffs - likely from when they were originally installed.
As I thought, there was a thin oily orange sludge under the base and evidence of surface rust. Not too bad though. will buff right out.
The screws on the ladder bar were buggered in the original photos I took. I ordered new ones.
If the tumbler doesn't come out of the hammer tomorrow after soaking, I will settle for flushing all with kroil. The pawls on the tumbler have a good amount of rust, which is why I want to take it off. I suppose I can try to do my best with fine brass wheel on a dremmel to clean it up.