Well, there's really not a particular all-in-one tutorial that would cover it.
It was a combination of techniques that involved the Clone Stamp Tool, the Brush Tool, and layer masks.
I did have to use an Alpha Channel selection process on the families hair, which was fairly easy given the bright highlights.
I just overlayed the new image over the old using the Transform function and the Move Tool.
You have to use the Clone Stamp Tool to remove/replace the Gazebo roof behind them.
Before.... new image on top.
During.........with the new image layer turned off.
Using the Clone Stamp and Brush Tool on a new layer between the new image and the old image.
After.....
Here is the Clone Stamp Tool and Brush Tool layer....
I also replaced the missing post by selecting the one next to it with the Polygonal Lasso Tool, then moving it with the Move Tool.
I then used a layer mask and the Brush Tool to blend it in.