Those keeper pins are tapered. After you remove the nut, take a ball peen hammer and tap them out of the hole. Be careful not to ding the threads, you may have to re-use them. Quite an easy job once you do one, you'll breeze through the next one. Double check the new ones to the old ones. You are probably going to have to hone the new bushings for the new pins. You should have a choice of machine shops that can do that for you and I suggest having them hot tank the spindles. It's so much nicer to have clean parts to work with.