I'm glad to hear that the music box was not destroyed in the flood,
but I would say that it's still not "out of the water".  The music box
should be attended to with some good preventive maintenance: oiling
of the mechanism using clock oil and a thin coating placed on the top
and bottom of the musical comb to inhibit rust.  This should be done
by a qualified musical box technician.

Treating the discs would depend on what their condition is after the
flood.  In general, I would clean them very well using a firm brush,
soap and water.  If they have rust, try to gently remove it.  They
should be then thoroughly dried off; a common hair dryer would be fine
here.  Finally, they should have a protective coating of oil on them;
you can use WD-40 as a fine mist (not the normal stream).

Eliyahu Shahar