Well...
I'm a Guy, grew up farming, and I'm sorry to say that this isn't MY favorite decor.
Your colors are too close together IMO...therefore DARK.
* You'd HAVE to prime the walls, then 2 coats of paint.
* It's either that, or change/paint the furniture!

Faron

I like the paneling, myself. Why not hang a quilt or a similiar large fabric panel behind the secretary? And then, line the back wall of the secretary with paper or something so it doesn't blend into the wall? Something colorful on top would also keep it from blending in.

Larger table cloth would cover more of the table top; less wood showing. Rug under the table would add more color, less wood.

You'd HAVE to prime the walls, then 2 coats of paint.
If you are going to do this,cleaning the paneling is probably the most important step,all oil,etc must be removed before priming.

I have less expertise than anyone here, but I would paint whatever I wanted to paint in a second. I waited too long to paint the panelling in my living room, and have loved it ever since I painted it.

I wanted mine to be an off white, so I washed off the dust, painted it with a product called "Bin", then painted it. Since the panelling was brown, and the Bin was white, I think I just put on one coat of paint.

I used a chemical mask when I painted the Bin because the fumes were so oppressing.

Sammy

Paint the panelling, no question. The furniture is not too dark, it's lovely. Painting the panelling a light color will enhance your furniture.

How about a compromise? Can you paint some and not others? Pick and choose so you brighten it up, but don't paint all of it? I also like ideefixe's ideas to bring more "light" into the room. And another agreement that if you do paint, do the proper prep and then prime first.