No other or further proceedings for the construction or repair of sidewalks, curbing or gutters and levying assessments therefor shall be necessary by the Service Director than the proceedings required under this section and Sections 903.03 and 903.04. In any case in which special assessments have been made on property for all of the cost of the construction or repair of sidewalks, curbing or gutters under such sections, such assessments, within the limitation of benefits and the limits of the taxed value of the property, shall be valid assessments upon such property.