The Reese Electric 5th Wheel Landing Gear Set part # RP500708 is only offered by the manufacturer as a set. That said, it is going to be recommended to replace both legs even if only one is damaged because this old leg/motor can put additional stress on the new leg/motor therefore it will be best to do both at the same time.
If you want to reuse the existing switch panel you are free to do so and you can just keep the one that comes with as a spare. view full answer...