Because of the trouble of having to open up the obs. hive and all that, I might suggest taking a frame of bees from the other hive, AND the queen, put that and shake a bunch extra into the obs. hive. Give the new queen to the regular hive. That way you don't need to open the obs. hive to take out a queen cate.
I just took one or two frames with eggs and bees, shook some extra, and let the obs. hive raise thier own queen. Not the ideal queen, but with only one or two frames to lay in she's been fine for 2 years now.
Rick