Ford People: Whats wrong with my truck?

The last few days the battery light has been flickering on and off. When I give the truck gas, the light stays on constant or it stays off constant. When I let off the gas and it is in idle, the light flickers. On the way back from town today, I was at a red light and I noticed all the dash lights and CD player flickering and the clock on the CD player was going on and off. The truck nearly died at the red light on me and after I turned off my headlamps, heat and stereo the truck ran good enough to get me home. Once home, I turned all of those things back on and the truck died. My guess is the alternator is out or bad because once the motor was off, the lights still worked off of batter power – although they were not fully illuminated. While i had the issue in town, all lights like gas gauge lights, speed needle etc., were jumping for flashing. Yeah, I know I should've bought a Chevy, but I have what I have... please give me some of your insight. Thanks.