Looks fairly simple - remove the screws holding the bearing block to the frame, then pull the bearing block off the end of the ball screw shaft. It shouldn't be very tight. Take care to support the ballscrew shaft so it isn't left hanging - it won't do it any good.

A clicking noise indicates that (probably), a ball is damaged in the ballrace. The bearings are usually 'standard' - once the block is off the machine. it should be possible to tap the bearing out using a metal shaft - place whatever you use to remove the bearing against the inside edge of the bearing.

Looking at your photos, there appears to be a small cover of some kind on the inner side of the bearing block - if so, remove this before pushing out the bearing - there may be a second bearing under the cover.

Bearings are 'standard' as a rule, and not particularly expensive. It is unlikely it is a special type, so simply measure the size (diameter, thickness and hole diameter), and get a new one - all the usual online bazaars should have them (eBay, Aliexpress, etc). You may even find them by searching for (eg) - bearings for 'machine type')

Keithw