My 1973 vw Beetle just had new alternator installed and driving home generator light stays on-Help!!?

I just had pans and new alternator put on 1973 beetle and drove it home aprox.40 miles.The car died at a red light and wouldnt start- i thought it may be battery so, i replced it and the generator light is on again. Should I replace something with that at the same time(solenoid,coil,etc.) Help!!