The diff comes out, stripped down, a new pinion bearing, collapsible spacer, seals etc. and a new modified drive flange. Then the pinion preload is set. The diff gets resealed and assembled and fitted back into the car. Once in, a new modified propshaft is fitted.
Lost count the amount of these I've done over the last year. At one point I was doing 3 a day for a couple of weeks, bloody killed me lifting them in and out every day!