yes, the cable goes to the lower connector in the D90. It is an open/close switch. You can see three cables because the nikon cable uses 3, but two of them go to the same pole in the relay. I just checked Amazon and the relay is 35 euros here in Spain. Kmtronics also sells the relay with no cover and this is cheaper.
You only need a remote Nikon cable/plug, nothing more.

Read More...