you need to put something like electrical tape around the barrel just in case you miss while hitting it. i dont think it matters which side it is knocked out from . you need to get a small lump hammer. you need weight and heavy impact to get that sight off.when you tap the new one in go slow and use a brass punch checking often to see if its lines up where you need it to be. you may also want to use the round part of a ballpein hammer to just lightly tap the edges over before tapping in the new sight. take your time and good luck!