Standing at the front of the lathe
remove grub screws completely from the collar on the left hand end of the spindle there may be 2 in sometimes (imperial sizes only )
remove grub screws completely from the pulley
place a piece of wood between the rhs end of pulley and rhs bearing housing.
if you have a blowtorch warm the pulley to expand its grip off the shaft.
now with a drift...brass copper or wood knock the spindle out towards the rhs
completely remove shaft lift out pulley
now on top of the bearing housings remove grub screws and knock bearings out towards the middle.
replace with sealed bearings
reassemble in reverse warm the pulley if its tight
watch that the pulley edges dont get caught and break off