For 15 months James Ostrowski, left, had a modest enough dream -- the gubernatorial nomination of New York's Libertarian Party. But last month something came between the Buffalo lawyer and his visions of matching wits with (or being ignored by) Mario Cuomo: a 900-lb., microphone-wielding gorilla named Howard Stern, who announced he was going after the party's nod. "I think I have a chance to win," said Ostrowski on the eve of the convention, held at the semicapacious Italian-American Community Center in Albany. "I feel Stern is using the party for his own purposes. I don't think he's that interested in politics. It's his diversion for the year 1994. There's something called principle. There's something called honor." There's also something called celebrity. The final vote tally: Stern 290; Ostrowski 34.