Of course there lots of thoughts on queen introduction, but I wasn't comfortable
leaving the discussion at the response I read.Requeening is much easier during
at least a bit of a honeyflow,
 
requeening a big mean hive is a problem, . If you can't or don't want to find
the queen, you could remove say 5 frames of bees and brood from the big hive,
and set it aside as a new hive.  Try to leave the queen behind, but in 3 or 4
days you will know where she is (where there are lots of emergency queen cells
started). Knock out the cells, and introduce your new queen into this easily
managed unit. Later, when you can find the queen of the mean hive, kill her and
unite the 2 units for winter. If for some reason the introduction doesn't take,
you still have the old meany, who will keep you going til spring. There are lots
of options and variations, but introducing when there is no flow is harder.
good luck