A. An appeal may be taken to the supreme court from the judgment at any time within ten days after entry of the judgment. The appeal shall be taken, perfected and heard in the manner prescribed by law for appeals in civil actions from the superior court.B. If no appeal is taken or if taken and the judgment of the superior court is affirmed by the supreme court, the judgment shall be conclusive as to the validity of the contract or agreement and the terms and provisions thereof, any bonds, taxes or provisions for reserves, and shall not be questioned in any court. All issues which were or might have been raised at the hearing on the petition shall thereafter be res judicata in all actions involving the validity of any of the provisions included in the judgment.C. The costs of the proceedings shall be allowed or apportioned between the parties in the discretion of the court.