[Viserion]

I don't know about the fading part as I don't have access to wow atm but this is what I use for the showing/hiding of a frame when a target exists:

function eePanels2:PLAYER_TARGET_CHANGED()
  if UnitExists("target")then
    THIS:Show()
  else
    THIS:Hide()
  end
end
eePanels2:RegisterEvent("PLAYER_TARGET_CHANGED")