Ignition tumbler

1984 Jeep CJ7, 84.000 miles, 258ci, fuel injected. Within the last week, when I turned the key off all my gages went off but the engine still ran. The first time this happened, I turned the key back on and off a couple of times and then it shut off. The second time, my wife was driving and I told her to do the same as I did but it would'nt shut off. So I had her put it in gear with the brake on to stall it. My key tumbler has been worn out, occasionally I could start it without a key and I could remove the key in the start and run position. I was told that the tumbler needs to be changed. I bought a new one but the instructions said to remove the steering wheel, etc.I can't seem to get to the mechanism this way. Anyone know how I can take the key tumbler out and replace with a new one?