Remove background on photos (deep etch)

Looking to have the green background removed for 6 photos and replaced with a grey like the example attached.

Final files need to be high resolution psd with option to remove grey background layer. Do not put the image in a circle, use example only as a reference for the shade of grey needed.

Needs to be completed today (within the next 2 or 3 hours). Will provide all high res files once awarded the job.

Thank you