Realistic Team Photo Head Swap

I have a single group shot of our boys’ team and one player missed the photo day. I need you to create a convincing duplicate of one existing boy’s body and then replace that body’s head with the high-resolution headshot of the absent player that I will supply. The finished image must look completely natural—skin tones, shadows, lighting direction and overall sharpness have to be indistinguishable from the original photo so no one can tell any editing was done.

You will receive:
• the original full-resolution team photo (JPEG)
• the absent player’s headshot (RAW and JPEG)

What I expect back:
• the final, ready-to-print team photo in high-resolution JPEG
• a layered PSD (or equivalent) so future tweaks are possible

Please work in Photoshop (or an equivalent professional editor) and keep the colour profile and dimensions exactly as in the source file. The final composite should hold up under close inspection and at large print sizes.