2003 Ford Taurus Dash Lights Intermittently On

For about nine months out of the year, my dash lights have only the left and right turn signal light illuminated - all the time. The other three months it works beautifully, and there is no explicable reason as to what makes it go one way or the other.

When I took it to the dealership, they wanted to replace the dash circuit board ($280 plus labor) because they said it was fried, but no one could tell me why they thought this. I passed and here's why. I have intermittent cutting out of my after-market stereo - occasionally cuts out for about a minute. And every once in a while, my driver's side window decides to either not roll down or not roll up.

All of these things hint to me of a loose connection somewhere that could've even been caused by the stereo install, but the issues didn't start right after this. Would you have someone try reinstalling the stereo to trace the wires or am I just silly for even thinking of that? Just don't feel like throwing money at the wrong solution since I just spent $1100 on an alternator and oil pan gasket replacement.