Are ceramic brake pads really necessary?
Ceramic brake pads just refer to the composition of the pad. Your 98′ Mustang came factory with this type of pads on the rear and the shop is only following the replacement recommendation of the factory. Ceramic pads should be no more expensive than any other pad, what they are trying to sell you is a Premium part. Ask for the mid-grade part and the price will be more to your liking.