2002 Celica electrical problem

I own a 2002 celica gt 1.8l 1zzfe engine, w/a bolt on turbo and a AEM fuel ignition controller. Its been sitting for 2 years but during those two years it was being started. With the exception for the past 8 months due to the battery going dead. So I finally returned back to the states to pick it up and it doesnt start so I replace the battery. It starts. The problem is, the odometer and tachometer and speedometer doesnt work, neither does the ac, windows, door lock, sun roof, and custom gauges. It does turn on if I redline while in neutral but the lightings are flickering but reading. I.E. The tachometer shows my rpm's as I rev. When I turn off the car and start it, the same problems occur. Whats my problem? Some people have been telling me its a bad ground or blown fuses. Im taking it to a shop sometime this week but I want to take it to a shop that I know that will fix it by me identifying the true problem.