An actuatable slidable panel assembly, a retrofit kit for converting a slidable panel of a panel assembly from manually actuated sliding movement to mechanically assisted, actuatable sliding movement, and method of retrofitting a manually operating sliding panel therewith are provided. The retrofit kit includes an elongate driven rail configured for attachment to the slidable panel. The elongate driven rail is configured to be attached to the slidable panel. A rotatable drive member is configured for operable engagement with the elongate driven rail to drive the elongate driven rail and the slidable panel along the direction of travel between open and closed positions.