Too many amps?

No -- if you put a high-amperage alternator on, it won't cause a problem. But why bother? It will weigh more and cause more drag on the engine -- both of which lower power by a bit and use more gasoline.

Yes -- if you put a big load on the alternator (High-output headlights + driving lights + big stereo amplifier) you could draw too much amps for a stock alternator. This would be bad.