Pontiac - Sunfire :: 2004 - Odometer Reads Error / Some Gauges Dead And All Lights On

-At first, the car stereo wouldnt turn off when the car was turned off (the battery died many times :P) -I learned my lesson, and manually turned it off every time I got out.

-Then the radio started acting weird an randomly shut off, switched modes etc.

-Then while driving one day.. the "Theft" light turned on while driving and the radio shut off. The odometer read "error". It would go back to normal, but stay for longer periods of time when it happened.

-Then the car had problems starting, AND the day lights wouldn't turn off 50% of the time (I had too unhook the battery)

-Eventually the radio just stopped working and wouldn't turn on, and ALL the dash lights stayed on while driving, with none of the gauges working, while the odometer reads "error".

-After about a week of that, I decided to remove the radio. That actually worked alot. The MPH gauge and the RPM gauge now work, the front lights are back to normal. The car starts every time!

-However, the Gas gauge and Temp gauge still don't work, and the lights are all lit up on the dash and it still reads "ERROR"

I know it can be many things, but what steps can I take to find the "short" or "bad wire" or fix the problem. I know the hard part, is actually figuring out what is causing it.