possible alternator, but I'm not sure on 1995 GMC Vandura 2500

It all started with the gauges going haywire, jumping all around. Then the radio kicked on and off and finally the engine died. I was able to restart it without a problem, but the speedometer says i'm going 60 when i'm going 20. It has died twice while driving and I'm not sure why. Does this sound like an alternator about to crap out, or could it be something else, like the computer or electric ignition?

It sounds like your instrument cluster needs to be checked, Speedo reading 60mph all the time, this can't be right.