When I push the cylinder release thumb button and pull out the cylinder, I get lots of resistance. And this is from an unfired, cleaned gun, so I know it's not grit or powder residue.

The pin in the center of the extractor seems to retract ok when I push on it with my finger, but it's leaves quite a scouring mark on the back of the frame. The release pin that the thumb button pushes forward seems to works ok too.Holding it downward does little to the cylinder make it easier to come up.

How can I fix this, or do I did to see a 'smith?

Check your ejector rod to make sure it's screwed in tight. It's got a reverse thread. If that's the problem you can tighten it. Make sure you support the ejector by loading empty spent cases in at least 2 cylinder holes and wrap the ejector rod with a rag and either carefully use a pair of pliers or lock it into vise jaws.

It's also possible the center rod is a tad too long. IF the screwing it in doesn't work check that. You should be able to press the rod to flush with the extractor with a reasonable amount of pressure. If you can't there is something wrong.

Also the yoke could be bent, though it would in that case NOT be consistently hard to open. That is easy enough to check by eyeballing it with the yoke all the way open and something lined up to give a visual constant as you turn the cylinder.

Yep, that was it. She's right as rain now. Thanks!