Their government can certainly print money endlessly, but it's like issuing more stock: it doesn't just make the value of that country go up, it makes the value of its stock (money) go down proportionately.
So the fact remains that Greece won't be able to buy all the things it wants without outside cash. And who is going to give it any now? If you just print money without limit, you'll soon find that there's nothing to buy with that money due to inflation.
Maybe they can copy Argentina, but when their finance minister's exit speech is basically "haha, later suckers!" I don't have high hopes.
If their currency were to lose value, their exports would become cheaper in relation to others.
This in turn would drive up exports.
Right now the euro is trading pretty much on par with USD.
Not likely that this is beneficial for the Greek economy, as it seems very dependent on farming and raw material extraction.