Okay, everything was going peachy for awhile. Till I found out my alternator was conking out. So I put the battery on the charger (it was LOW) and put it back in. Now, the stereo I just put in won't turn on. Would putting the positive cable on the battery first somehow blow the fuses? Or is there something else wrong?

 

I found out that it was the ground, thanks to Clark. Plus, I learned that my headunit is picky about being grounded first before being plugged in. I switched the ground to the one of the shifter bolts and it fired right up on the first try.