Regardless of the estimates the camera is worth more to you. While it might not add to the monetary value it does have the Nadar connection and you know it passed through the shop. There's some great cartoon's he did of himself online and some are worth printing & keeping with the camera.

On a more practical note, see if you can make an adapter to take standard 5x4 darkslides, I've made an adapter for a roll-film back that slips in like a plate holder on my Quarter plate, there may be enough room to do similar with your camera. Then I made a second lens board to use a more modern lens.

I've seen the Sands, Hunter tailboard camera with a Thornton Pickard shutter attached to the lens board, but they can also be fitted to the front of the lens.

Let us see how you get on with it, it's nice camera to own and it'll be fun to use.