2004 Mercury Sable "Clicking" from steering colum

I changed the battery today and so far so good. THe only thing that still don't work is one of the key pads to unlock the doors.

The symptoms from an earlier post match mine:

Electrical problem
2004 Mercury Sable 6 cyl Front Wheel Drive Automatic 58000 miles

I've read a couple columns where the symptoms were similar to what's happening with my car.
My car was fine as I drove around all day. I stopped for 1/2 hour then went to run more errands. I heard aloud "pop" when I turned the key in the ignition and then nothing.
The engine never turned over and then all the electrical issues began. The radio light was real dim, kind of fading in and out. The remote would not open the doors and I couldn't roll up my windows.
I attempted to turn the ignition again and still nothing. When I pulled the key out of the iginition, I hear a distinct clicking noise coming from the sterring column and both the speedometer and tachometed arrows jumped up and down by themselves!

I've noticed that some times the dome light will come on when I open the door then it will dim after I attemp to turn the iginition.

I read a couple of threads onliine where some of the symtoms were very similar to mine with the exception that my car won't start. I seen more then once where the recommended fix was changing the transmission range sensor. My car only has 58,000 miles. Am I in the ballpark or should I be looking elsewhere?

IS GETTING THE BATTERY REALLY THE FIX, OR IS THERE ANOTHER ISSUE?