Here are some things i would try if the car was here.
1. Remove plastic clips and pull out the front tray to access the battery.
2. Make sure battery cables are secured properly to the battery and are nice and clean.
3. Trace the ground wire until the point where it attached to the frame. You should remove this bolt and using a small piece of emery cloth, make sure the surface is nice and shiny. Re-attach bolt.
4. Using a common voltmeter, check the voltage level of the battery.
5. If it is below 11.7v, you need to charge it with a good-quality trickle charger.
6. At the Battery Junction Box (BJB) - the fuse box on the driver's side of the battery, check fuse F1.15. This is the alternator fuse. It may be blown.
7. For kicks and giggles, go to the rear passenger side of the car with a flashlight. Get down on your knees and shine the flashlight in 2-3" to the right an 1-2 inches below the right exhaust tip. You are looking between the transaxle and the right catalytic converter. Your flashlight beam should be on the starter solenoid and the big battery cable going to it. Make sure this all looks good and that nothing is melted or no exhaust components are too close to the battery connection on the solenoid.
8. With you battery freshly re-charged, once again get an ignition-off battery voltage. Start the car.
9. Let the car idle. Re-check the battery voltage. It should be 13.8-14.0v. If it is, your alternator is working properly. (I would seriously doubt that the car need a new alternator in the first place.)
10. If all this checks out you have either a bad battery or just one that needs charging. Note that these batteries do NOT like to be brought back from the dead.... Regardless, try slow-charging it with a good quality trickle charger.
11. Your gauge "problem" is because the battery voltage is low.
Let us know what you find. Oh, and if you worried that you got a lemon or something, just relax. These cars are very reliable and once we get this minor glitch resolved, I'm sure you will have a big smile back!!
PM me if you want to chat by phone...