Remove all screws from the underneath of the swing head.
Open the battery cover and remove the 4 screws inside.
The top should now be loose.
Carefully rotate the top out of the way so you can access the swing gear box.
Remove the 2 screws holding the gearbox down.
Lift the gearbox up and out.
You may have to move the swing for the spring to clear the gate of the swing mechanism.
Remove the 3 screws that hold the gearbox together.
Pull the spring straight up from its mount and set aside, noting which way it came out.
Lift up the rotating mechanism and set aside. Lift up motor and pull off the worm gear.
Cut and strip the wires going to the old motor.
Install worm gear on new motor and set in place. Strip the wires on the new motor,
and using the supplied wirenuts connect the wires together.
Make sure that the wire going to the + of the old motor goes to the + of the new motor.
Make sure you test that everything functions before you close it up for good.
Reassemble the gearbox and secure it in the swing.