That's the problem: The flooring is a warm color and the walls are freezing! Mustard that's more golden than one more yellow/orange. The white woodwork/trim needs to be painted a warm white also, imo.

I see no need to tear out the wainscoting but I wouldn't select a paint color until either you have a sample of the granite for reference or it's installed.

I agree that your flooring seems to call for a warmer wall color, and mustard would likely look great, however, there are many variations of that color, and as annz mentioned, it might be best to wait until you have a granite sample. I also agree with allison that a creamy colored woodwork/trim would work better than the bright white, given the warm colors you're migrating toward.

Jan