Mark,
You are doing the right thing by asking here about things you were informed. If the same person who suggested that you change to an alternator is the same person who suggested you change from 6v to 12v, you should be wary of further suggestions (just listen politely and do as the British do in such situations, just give a friendly/polite nod and say "indeed").
GrandpasTruck has the right response. If your generator is working fine and you do not need more amps, stay with the generator.
