99 Tahoe with some issues...

[stumped99]

I have a 99 Tahoe that had a Viper alarm and remote start installed before I purchased it. This vehicle was also wired for sound using Directed components; which most know they build Viper. I recently installed a cheap cd receiver for the wife, and the next day it refused to start and run. Towing, fuel pump, relay, radio disconnect, and several busted knuckles later, it still won't run. It starts then dies immediately. Also the gauges stopped working. As if they were frozen. Fuel reads half tank, voltmeter is bottomed out, oil pressure is normal, and water temp is normal...even with the key off. Did I destroy the ECM while installing this radio? Any help would be appreciated. Thanks.