The plastic button cap on my D300 broke leaving me with this. Nikon estimated 300 to repair. The camera isn't worth much more than that.
I was able to touch a small piece of wire and short across the thin line traces and activate the buttons so I knew they worked.
I bought a new QUAL WB ISO Button for 29.00 from an ebay seller in China because Nikon won't sell you parts.
Back of the button assembly.
Remove the bolts from the old cover.
Lift the button contact cluster board up.
Remove the 2 screws on the new part.
Remove the button cap from the button contact board.
Carefully pull the button contact cluster board away from the camera so it's free enough to expose the 2 screw holes. The ribbon cable will put out of the camera enough to do this.
Take the new button cap and line it up to the button contact cluster board. It will only go on one way.
Using a jewelers Phillips screwdriver (mine was magnetized) screw the 2 screws through the button contact cluster board into the new button cap. They should go in snug. Tighten them firmly but don't strip them out. If you do have a stripped hole you could use some glue to secure the fastener.
Carefully push the slack section of the ribbon cable down into the body.
Line up the button cap so the vertical line aligns with the 's' and snap it into place. You will feel it click. That's it. You saved yourself almost 300.00.