Empty FuseBox Terminal

So it sounds and looks like my tach is supposed to plug into the "shinny" terminal?
You've got the real thing on your side of the screen. You'll have to tell us if what you have matches what we've posted.
A vacuuming up of the tinder, and then a gentle cleaning of the insulation wouldn't hurt. Just a damp cloth should be enough. Connections may need something more but if that shiny is any indication, the contacting surfaces are not in bad shape.