To remove the ignition switch, first remove the outer bezel. I believe there are two slots in the bezel - a pair of snap ring pliers or needle nose pliers should work to loosen it. I've seen different style bezels used so yours may differ.
Behind the dash, the switch is held in place by two 3/8" (I believe) nuts. Remove them and the switch should drop out. Then, mark each wire's location on the switch and remove them.
Don't forget to disconnect the battery first!