I'd start with changing the wall color. I think a warm white on the walls would make a lovely difference, and I would leave the wood trim. I would also not paint the fireplace, but focus on brightening the room overall and cozying up the decor. But for sure, paint the walls first.

I would paint the trim and mantle white to match the rest of the house. It would create a more cohesive look. I also find that white trim is less limiting than wood when it comes to selecting wall color.

Thank you both for your input! Is there a creamy white that you might recommend?

If I did decide to paint the trim, would the windows have to be replaced as well, or is there any argument that I could keep them brown?