Image editing - cleaning up a vintage art file

I am looking for someone to clean up an image in Photoshop.

The art file has a lot of discoloration and I would like this to be cleaned up to be more consistent with the lighter areas of the image. This needs to be done carefully to protect the integrity of the original image and detail.

It is vintage art so I do not want it cleaned to the point that it loses its character.

In the attached the full original image and a sample where I have market with red areas where I would want the background cleaned and looking more like the areas marked green so using a spot healing tool to sample a good part of the background and fixing the areas that are market red ( these are just some examples to guide the process) to do this for the whole image.