Replace the ignition tumbler (mechanical part) or the electrical part? Here's the mechanical portion...
Disconnect the battery.
CAREFULLY remove the lower part of the clamshell plastics around the column. There are Torx screws recessed deep into the holes in it - lay down on the floor and look up, if I recall there are 3.
CAREFULLY pry the bezel off the ignition switch. Some of them come off easily, some fight to the end. It's got plastic tabs surrounded by a metal band that hold it to the edge of the tumbler. I like to use a door panel (soft fork style) tool for this job. You have to be gentle in order to not break the surrounding upper clamshell plastic.
Look closely at the underside right of the upper clamshell plastic; there's another Torx (again, if I recall, this one will be an external Torx) screw holding it down, may also be one on the other side. Sorry I can't be more specific but it's probably been 6 months since I've done one of these. Lift the clamshell plastic off.
Now that you have the cast aluminum housing of the column exposed, look at the top of it just over where the tumbler lives. You'll see a small hole. Put the key in the ignition and turn it to the start position; you'll see a tab appear in the hole. Press it with a pick. Pull the tumbler out.
The replacement will just pop right in.