The trustees of a road improvement district shall, within thirty days after the effective date of the merger, submit to the city or village a written accounting of all assets and liabilities, contingent or fixed, of the district. Unless the city or village within six months thereafter brings an action against the trustees of the district for an accounting or for damages for breach of duty, the trustees shall be discharged of all further duties and liabilities and their bonds exonerated. If the city or village brings such an action and does not recover judgment in its favor, the taxable costs may include reasonable expenses incurred by the trustees of the road improvement district in connection with such suit and a reasonable attorney‘s fee for the trustees’ attorney. The city or village shall represent the district and all parties who might be interested in such an action. The city or village and such trustees shall be the only necessary parties to such action. Nothing contained in this section shall authorize the trustees to levy any special assessments after the effective date of the merger.