Sections 407.585 to 407.592 shall apply to any new farm machinery sold after January 1, 1988, but no provision of sections 407.585 to 407.592 shall operate or be construed to invalidate, impair, or otherwise infringe upon the specific requirements of any contract between a dealer and a manufacturer entered into prior to September 28, 1987, and which is in effect on September 28, 1987; provided, however, that in any case wherein warranty repair work is performed for a consumer by a farm equipment dealer under the provisions of a manufacturer’s express warranty, the manufacturer shall reimburse the dealer at an hourly labor rate that is the same or greater than the hourly labor rate the dealer currently charges consumers for nonwarranty repair work. The dealer may accept the manufacturer’s reimbursement terms and conditions in lieu of the above.