Hi Christina,
I took the opposite path from Manfred and put the basic source on the bottom layer and the donors above.
The layer named Face was aligned on the woman's eyeglasses and the whole face revealed. Note the very black mask with the little dot of white.
The layer named Wave was rotated to orient the two horizons and then adjusted to the waving man's neckline. As you can see from the white in the layer mask, I revealed quite a bit: from his neckline, down his body (just missing the team device on his shirt) and the forward leg as well as the (camera) left edge of his rear leg all the way to the edge of the frame. These are done with a soft edge brush so there is a deal of blending here.
At the end of the day, no heads were swapped.