Replacing Ruger rear sights is a simple operation: To remove, back off the elevation screw and drive out the retaining pin. Remove the old rear sight and springs.
To replace or install new, use a dab of grease to hold the springs in place and set the sight in position. Screw down the elevation screw and drive in the retaining pin. If the pin is too loose, bend it slightly and drive it in.
This is an all steel replacement sight from Gary Reeder.