Seamless Photo Composite Needed

I have a finished photograph and a separate head-and-shoulders shot of a person who was absent when the picture was taken. Your task is to drop that person into the main image and blend every edge, colour tone, shadow and highlight so convincingly that no one can tell the scene was altered... (Budget: $30 - $250 USD, Jobs: Color Grading, Illustrator, Image Analysis, Image Processing, Photo Editing, Photo Retouching, Photoshop, Photoshop Design)