Just wondering if you still need help with this. I attached a sample below of what I have done. The short explanation is to use a mask on top of the original image, rather than changing the base image altogether.
Just holler if you need more descriptive instructions. And just so you know, I am self-taught user, so I make no claims to knowing the best ways to do things in Photoshop. One thing is for certain a digital pen and tablet is much much much easier than a mouse when tracing to make the mask.
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