When installing a glass bed, what do you change?
The most common way to install a glass bed (assuming it's literally a piece of borosilicate glass) is with binder clips. Glass is an insulator, so you may need to adjust your bed temps by a few degrees, and it will take somewhat longer to warm up.

You shouldn't need any firmware changes, but will need to adjust whatever z homing you do. If you have a limit switch currently, you'll need to move it by the thickness of the glass. If you have an inductive probe, it should still continue to work, but your z-offset will need to be adjusted. If you have BLTouch or a piezo, nothing should need to change there.