Traction Control Off and Brake Warning Lights

Recently, I began occasionally having problems turning the car off and removing the key from the ignition. Managed to get it to work by either moving the steering wheel or restarting the car and turning it off again. This stopped happening for about a week, but then something new started: Once in a while when driving and coming to a stop, antilock brake felt like it was kicking in (on dry pavement) and traction off warning light and red brake warning light (NOT the antilock brake warning light) came on, then went off after a couple of seconds. This happened several times in a week.

I noticed that at the same time, the trip odometer feature would automatically flip from the normal mileage indicator to the trip odometer feature without my trying to change it. Finally, one day last week, the key would not come out of the ignition again, but I got it to come out after I moved the steering wheel, etc. Then drove a few miles and when coming to a stop, the service engine (amber) light, the traction off light, and (I think) the brake light all came on. I also lost the power steering.

Not sure if the car actually stalled or not because it all happened so fast. I think I turned the car off, actually, then turned it right back on again. The warning lights stayed off and I carefully drove the rest of the way home, about 1/4 mile. Had the car towed to repair shop. They've told me they think it needs an ignition cylinder or switch but also that it's showing a code in the brake system's computer but they have not been able to isolate which of the four wheels it's coming from. Any ideas? I've read some similar things on this and other websites, but in those cases it seems to be the antilock brake warning light that came on along wtih the traction off light, whereas it my case I think it was always the regular (red) brake warning light that came on.