I just did mine on my '91 300d. The complete instructions are listed, probably on the diesel forum. The hardest part was once the sending unit is out, getting the black bottom piece off. Like someone else said, sacrifice a tiny flathead screwdriver, cut out a middle piece from it with a hacksaw or Rotozip. You might even be able to use 2 nails, held tightly together in a vice grip. But once loose, the opposite end (the guts of the aluminum sending unit) come out so be ready, just a few inches away from a cushioned surface for it to fall on.