The coordinates of the actual site are 43.137675, -88.206257, which you can plug into Google maps.
Park at NAPA Auto Parts or Sussex Inn in Sussex (hence the name "sexy" or "sussexy" quarry) and walk down the Bugline trail (otherwise known as the sidewalk on Waukesha Avenue). You'll pass underneath a train bridge. Follow any trail through the woods, but the easiest access is ironically right by the "No Trespassing" sign. Before you turn in, make sure there aren't any other walkers that will notice your venture into the wilderness. Once in the tall grass, walk straight. You'll pass over some train tracks. Keep walking. There should be a narrow trail to follow. If you keep going, to the left of the electricity poles should be the quarry. Good luck!
Have you been to this quarry? What did you think? Leave any tips of your own or observations in the comments to help other explorers!