My IROC has an electrical problem

I have an '89 IROC Camaro with 89,000 original miles and a 5.0lt engine. Most of the engine is still original. We just had to replace the radiator because it got a hole in it. When we went to start it after driving it to a oil change the next day, it will not even turn over, it does not even click. We replaced the started, that did not fix the problem. We checked everything mechanical with the car and we have even narrowed it down to electrical wiring probably. Could you stear me in the right direction of where to start looking for the problem, or what type of place in Orlando, Florida, that I should look at to take my car to to have them fix it?

thank you.