Had to replace tho old spray arm with the new part which has a recessed pop up, The recessed pop up provides clearance to accommodate a current (newer) design lower rack. Removed the old spray arm and installed the new spray arm according to the provided instructions.
Most difficult step was to pull out the unit to replace the couple at the motor/pump by lowering the motor. Straight forward but involved. Involvement included disconnecting water supply line, drain line and electric. Motor/pump unit dropped easily and change out of the couple was simple.
Took me more than 2 hours because it was my first time ... could repeat in about 1 hour if I did it again.