With a little more research I found Bob Wright's post in the gunsmith forum on how to remove/replace a Ruger rear sight. Quite easy. It was actually harder to install the Trijicon MS22 base place for the Trijicon RedDot sight 'cause the mounting screw which goes down through the plate into the rear sight screw hole was about .070" too long. Good thing I had a supply of 150 grit and 1500 grit wet sand paper to shorten the screw. Then, wah lah! Neat that the mounting plate has a rear sight slot akin to a rear sight. Now, I don't know how well it alighns with the front sight, but we'll see soon enough.