VR6 impulse sender - easy to change?

Hi

My Fiancee owns a mark 3 golf VR6 and last week it was diagnosed that the "engine speed sender" had gone. I've called up VW and they told me that it's know as the impulse sender.

Now they have one in stock but I have no idea where on the engine this part is and how easy it is to change.

Can someone point me in the right direction please?

Thanks