the vibration is likely your tie rod ends or drag link, have someone rock the steering wheel back and forth while you are under it. Sometimes you can just tighten the nut down a little more and get a little more time out of it.
Ont he shutting off, I don';t realy know but I would think it is some kind of short or something in a wire in the steering column. Does it cut off if you turn the wheel while sitting still?
There are some links to sites on here about tearing into a steering column, I'll try to find some for you while you wait for others to chime in.
88 MJ I6 4x4 Stock my hauler - Sold
98 XJ I6 4X4 Stock my son's DD
06 12V Purple Barbie Jeep my daughter's DD :-)