first, I will assume that you have a method of getting up there. Don't try to feed the halyard itself. Use some light nylon twine [or something similar] with a fishing weight tied to the end. Feed it down through the top and have someone waiting at the exit slot with a wire hook made from a coat hanger. Make sure that the boat is heeling to port and that your other halyards/topping lift are all pulled tight. This MAY prevent you from getting a cross.
Dave