Thanks for the tips. I did a bit more study last night, and decided to try the procedure noted for a cage forcibly rotated past its stops. That seems to have done the trick, though I won't know for sure until I get a chance to take it for a shakedown ride this weekend. But with no load, it appears to be shifting smoothly, and such.

Now I just need to measure the chain stretch to see if I need to replace the drivetrain anyway... ;-)