Replace Image Background Seamlessly

I have a photo that needs its existing backdrop removed and replaced with a new one I will supply as a high-quality JPEG. The subject must blend naturally into the new scene—edges crisp, lighting and shadows matched, no fringing or obvious cut-lines.

Please deliver the finished image in both flattened JPEG (maximum quality) and layered PSD or PNG with transparency so I can make future tweaks if needed. If you use Photoshop, keep nondestructive layers; if you prefer another tool, ensure I still receive an editable version.

Let me know your turnaround time and a quick note on how you handle color matching to guarantee a realistic result.