The block and the nut were heavily corroded. Removing the old nut was very difficult, because the basket was free to rotate, using a spanner wrench just rotated the whole assembly, including the driveshaft. So I had to tap the spanner nut off with a hammer directly, striking it just right so it was spin relative to the block. Once off. I pulled the basket out and again had to use a hammer to tap the block off the shaft (WD40 was used liberally in both cases). I cleaned the shaft with a steel brush and more WD40, and cleaned the receptacle of all debris. Then it was very easy to put on the block, the basket, and tighten down the spanner nut.