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.

You will receive:
• The original high-resolution background photo.
• A high-resolution PNG/JPEG of the person to be added (shot on plain background).

What I expect from you:
• Careful masking and edge refinement.
• Precise colour matching and lighting adjustment so the new subject shares the same ambience as the scene.
• Natural-looking shadows and reflections where necessary.
• A final flattened JPEG/TIFF ready for print and a fully layered PSD so I can tweak elements later if needed.

I’m happy to answer any quick questions about pose, scale or placement before you start so we can get this right in one pass.