Is there any way to have the sensors for dashboard lights and digital interface tested? The guys at Sears said they didn't like the sound of my car though the fluids were all fine. It's funny they low rated my brand new battery too so I don't know. I took it to an autozone and had the computer checked but it rang clear bill of health.
When you first turn your vehicle on, the vehicle itself does a "Power On Self Test" or POST. When you turn your key from off to the run position (before you start it up), all of the dash lights which are usable will light up. You should get used to which ones light up and keep those in the back of your memory. If a bulb should go out, you'll notice the difference and know one is out. For the 05 Mustang, the dash lights should look thus:
Most of the lights in the dash should either light up with key on (mainly the safety ones like ABS and Air Bag), or you can make them turn on by doing different things (like starting up the car and not having your seat belt fastened to check the seat belt light).
If you took it to AutoZone and had the computer checked for any codes and it came up clean, you probably won't be seeing any indicator lights on the dash anyway.