Both the front and rear sights of a Springfield XDM 45 ACP can be replaced by using a sight pusher to remove the sight in question, followed by installing a new sight in its respective front or rear slot and adjusting it to line up with the other sight. Using a dedicated sight tool is generally more reliable than dislodging the sight by force, especially in the case of XD guns, whose sights are uniquely difficult to take out.
The first step of any XDM sight removal process is unloading the gun and separating the top section, known as the "slide," from the rest of the weapon. The slide should generally be wrapped in cloth to prevent scratches, then inserted into a sight tool using the proper clamp slots and adjustments according to that tool's instructions. Sight tools can be used to remove an existing front or rear sight from the slide, or adjust a new sight that has been inserted into the gun.
When installing a new sight in a handgun, make sure the front and rear sights line up properly, so the weapon can aim effectively. The rear sight should be positioned in the direction you want the weapon to fire, while the positioning of the front sight in relation to the target depends on the sight and the firer's intention. Usually, handgun owners use the "combat hold" of the front sight centering on the target for quick self-defense.