Update: went ahead and replaced the heated steering wheel control module (the other thing on my list of things to do today on the car) which involved disconnecting the battery as I don't feel comfortable working on airbags live... got that done and went for a drive. Car ran a little off for a while but after maybe 10 miles or so (readapting?) it actually started running better than it ever has in my ownership. I got a couple bottles of Techron (on sale at Advance! woohoo!) put one in and filled the tank up. Keeping fingers crossed? May check #6 plug again next weekend if it's not cold and crappy out. I really hope this is the end of maintenance/repair for a while, as I've completed my maintenance checklist and was really hoping to be rewarded with a good running (mod-ready?) car.
have no current codes showing, FWIW, but I don't know if I've driven far enough for any to have been thrown or not.