Fine Art Image Background Removal

I require a professional photo editor to remove the background from a single image. This is a photo of a collage that also shows the white grid lines of the copy stand used for the photo - unfortunately, it is the only image and the original collage has been discarded. The final image will be a fine art photo print, so a realistic effect is needed. It's important to replace the original background with a solid white background that's sampled from the existing one, without any grid lines. So, don't sample the white from the grid lines but use the slightly darker background instead to show contact with the cut out collage pieces. The final print size might be as large as 16"x24" so upsampling may be necessary.

Ideal Skills:
- Expert in photo editing software (Photoshop, Lightroom, etc.)
- Experience with fine art photo editing.
- Attention to detail and precision.
- Ability to deliver a realistic effect.