The referendum shall be conducted, and the Governor or any other state agency or state official now or hereafter authorized by federal law shall designate an agency or individual to supervise its conduct, in accordance with the requirements of Section 218(d) of the Social Security Act, on the question of whether service in positions covered by a retirement system established by the State or by a political subdivision or agency thereof should be excluded from or included under an agreement under this chapter. The notice of referendum required by Section 218(d)(3)(C) of the Social Security Act to be given to employees shall contain or shall be accompanied by a statement, in such form and such detail as the agency or individual designated to supervise the referendum shall deem necessary and sufficient to inform the employees of the rights and benefits which will accrue to them and their dependents and survivors, and the liabilities to which they will be subject if their services are included under an agreement under this part. Such statement shall include a general explanation of the modification, if any, of the existing retirement plan that may result therefrom. It is not intended that any modification of any existing retirement plan must result, nor that a plan of maintaining full benefits of the local system together with full benefits of the federal system shall be precluded.