Need help with picture

Ok so I need help with getting just the face of a friend onto the body of the quaker oats guy.

this is the picture of my friend. My friend is the guy. So just his face on the body of this quaker oats guys.


If it's possible I need it by Saturday. I really hope someone can help since I am insanely inexperienced with Photoshop and this is a surprise for him (inside joke)

Thank You to anyone that helps!!!!
Not perfect by any means - but will this suffice?

Sorry - I missed the shadow cast by the hat.

Thanks. In this case wasn't that hard, just selected the skin, created and empty layer and painted with the colour i took from the original, adding fusion mode colour to new layer and finish.
Thats why I love this forum - always something new to learn - thanks for the explanation.