Nissan Repair: Reversed battery, stereo radios, car wont start

Question
I have an 85' 300zx that my friend accidently put the battery in backwards. (+ to - and vice versa) The car wont start and the voice on it that tells me different warnings about the system isn't telling me anything at all. I Know it should be telling the fuel level is low because theres not a lot of fuel in it. but, I have changed the plugs and checked the intake. i think it fried my E.F.I. system so it wont start. am i correct in this guess? Thank You.

Answer
Shane,

You pretty much guessed it.  First, I would check and replace all fuses and fuse links that are blown.  Second, if there is still no start the ECM is probably fried.  Replace it and then you will have to go through each system that is blown.  Stereo radios are prone to internal failure if the battery is installed backwards.  Next, check the alternator to see if it still puts out voltage.  Should be 14.2 volts running the engine at 1000 RPMs.  Email me back if you need more information.