1999 Ford Contour Electrical

Hi. Hope you can help. I bought a used 1999 Ford Contour. Replaced water pump and radiator over flow unit, replaced the windshield, I few cracked hoses and clamps and the car ran excellent. I drove over 1500 miles with no problems. Then I had a stereo installed (wasn't one in the vehicle & never had been but the harnesses from Ford were there). The day I picked up the car from audio store, I noticed my battery dash light went on and would flicker during the day and at night would stay on. Took the car back to audio store and they said that I had to "reset" the battery. So they unhooked the battery, hooked it back up and great, no battery light. A few days later it started flickering again and sometimes stayed on. Then one day, I was on the freeway and all of the dash lights went on, i.e., ABS light, Engine light, Brake light, Battery light and lights I don't even know. The car lost acceleration, pulled over and called AAA. Explained to AAA driver what happened with stereo and he suggested I unhook the stereo that it may be wired wrong. The vehicle wouldn't start again and was completely dead. I called the audio store and they suggested the same thing and to bring it back in when I got home. I did. Car started right up. Few miles down the road, the battery light went on again. Got it home and took it to the stereo place. They told me I had a bad battery and wouldn't accept responsibility for anything. I bought new battery and car ran great for 2 days and light back on, however, after a few days of short trips, the ABS BRAKE light starts blinking and the car stalls (doesn't matter if I'm stopped or driving) it just stalled and wouldn't turn over. This time had the battery cables replaced and all of the fuses were checked and everything was in working order again. (Also, when the vehicle's dash lights went on and the car stalled, several fuses were blown: dome lights, beeping noise when doors are opened and electrical mirror adjustment fuses) Can you possibly tell me what's causing the car to keep stalling? I read the manual and according to the manual and the symptoms, it appears I either have a bad ECU, a bad solenoid, alternator, bad connection, etc? I understand it could be a million of things, that's why I don't want to take it to a Dealership because I only paid $1,500 for the car and already have that much invested. I really don't feel the cars worth dumping another $500-1000 into it (170000 miles). Especially, if it one of those "lemon" vehicles that you spend $20k for a $2k car when it's all said and done with. I've been there before and then you don't want to get rid of it because you have so much money in it. Is it fixable? Can you estimate the cost? Any suggestions or "your knowledge with these vehicles" would be helpful as to whether I should fix it or not. Thank you for any suggestions or comments you may have. KH.