(a)   Whenever a nonconforming use of a building has been changed to a more conforming use, such use shall not thereafter be changed to a less conforming use.
   (b)   A nonconforming building which has been damaged or changed to the extent of more than 50% of its fair market value by fire, explosion, act of God, or any other cause shall not be restored, except in accordance with all zoning regulations of the zoning district. In the event a question may arise on the fair market value of such a building, the same shall be determined by three appraisers: one shall be selected by the Governing Body, one shall be selected by the owner of the building, and the third appraiser shall be selected by the two selected appraisers. If the first two appraisers selected cannot agree on the selection of the third such appraiser, the Judge of the appropriate court shall be requested to appoint the third appraiser. The decision of the appraisers, or a majority of them, shall be final and conclusive and shall be binding upon all concerned to the purpose of determining whether the damaged property may be restored. The cost of such appraisal shall be paid by the property owner.