Any official who is eligible to participate in the supernumerary program provided by this chapter, and who is participating or eligible to participate in any other state or county retirement program, shall elect whether he or she shall participate in the supernumerary program or in the other retirement program. Election to participate in the supernumerary program shall be made in writing to the county governing body of the county in which the official is serving within 60 days following April 22, 1994; or within 60 days after taking office as the official, whichever last occurs. If the official is participating in any other state or county retirement program, he or she shall simultaneously withdraw from that program. Upon election to participate in the supernumerary program, the official shall immediately pay to the county tax collector or other official charged with collecting ad valorem taxes, for each prior year of eligible service to which he or she is entitled credit, that sum as he or she would have paid had the official been participating in the supernumerary program during that year of service, and the tax collector or other official shall distribute that sum as provided in Section 40-6-4. The official shall thereafter be subject to the other applicable provisions of this chapter.