I've sailed engine-less quite a bit, but not on purpose... not without an engine, just with an engine that was in "less" then working condition!
I would love to eventually have the time and skills to go totally without an engine, but for now, I can't, so I rebuilt an engine instead So far it's working much better (knocks on wood)
Unfortunately I can't give a whole lot of advice, nothing you probably don't already know, I'm no expert. There used to be a guy in the Seattle area that organized the Oar Club, a club for engineless sailors, but the site seems to be defunct now. From the googling I did, looks like he moved to Hawaii or something, and no one else took up the cause. Perhaps it was a club of one?
Good luck, I'm interested to know how the sculling oar works out, I plan to build one soon. Seems like a good compromise.
While I am decently good at engine repair, it's not something I enjoy. The other week I was working on an outboard on another boat, when my truck broke down. Twice. In one day. I got them both running, but I ended up singing a little song I made up that went something like "I hate engines yes I do, cars and trucks and boat motors too!"