Hoopla, hype and headaches. New York is ready for Liberty Weekend. "The party of the century," says Mayor Edward I. Koch of the $30 million four-day extravaganza to celebrate the Statue of Liberty's centennial.

Six hundred portable toilets have been assembled, 5,000 subway cars and 2,550 buses are geared to run, 40,000 boats are expected in the harbor, stores are overflowing with Liberty kitsch and the city's taxi drivers are threatening a weekend-long strike to protest a freeze on fares.

City officials predict that 7 million to 13 million people could show up -- although not all at once -- for the July 3-6 events. That is twice as many as turned out for the 1976 Bicentennial, and millions more, in this city blase about crowds, than during the pope's visit, the Brooklyn Bridge centennial or the 40th anniversary of the United Nations.

The celebration includes a parade of tall ships through New York harbor, the largest fireworks display in the history of the nation, three large concerts and a giant street festival in lower Manhattan. All the events are to be televised live.

"When the best city in the world throws the best party in the world, the entire world is invited!" Koch said at a recent news conference, brushing aside doubts about the city's ability to absorb the masses.

He had a word of advice for tourists, however: "Do not play three-card monte," the sidewalk specialty of city con men.

Travel agents reported a rash of cancellations and concerned phone calls after the U.S. bombing of Libya, but many apparently have reconsidered and rebooked, the agents said. In his news conference last week, President Reagan said he was concerned that the festivities "would be a very inviting target for those who hate us in the terrorist ranks and think that they might be able to embarrass us that way." However, he added, "I also have a great deal of confidence in our security people."

The city has announced that it will call up about 12,000 extra police officers for July 4-6, 6,000 on the day shift and 5,900 on the evening shift to control crowds. Police Chief Benjamin Ward said last month that department officials had held more than 75 meetings on security with the Federal Bureau of Investigation, the Coast Guard, the Navy, the Customs Service, the New Jersey State Police and other agencies. A task force to coordinate intelligence networks was set up.

New York's 100,000 hotel rooms are mostly booked, but officials expect space to become available in the next two weeks if tour companies are unable to sell all the rooms they have reserved.

"Remember what happened at the Los Angeles Olympics," cautioned Jack MacBean of the New York Convention and Visitors Bureau. "Hotel rooms and tickets went begging . . . . We don't want people to be scared away by stories that we are fully booked."

Interviewed on a Voice of America talk show a few weeks ago, Koch told callers from as far away as Sweden, Kuwait, Australia and Israel, "We're accustomed to crowds, and even if they tell you there is no room in the hotels, come anyway. We'll find places to stay, even if we have to open the parks."

That sent city park officials -- who have never allowed public camping -- scrambling for suitable spaces. Tent sites for 5,000 people are set aside in Flushing Meadows-Corona Park in Queens, but so far only 261 campers have reserved space. Recreational vehicles can park on Staten Island, but so far only 271 of the 1,200 sites are taken.

At the city's Transportation Department, spokesman Victor Ross warned, "We hope all motorists will observe the 11th commandment: Thou shalt not park in the city." Several major arteries will be closed to traffic during parts of the weekend, including the Henry Hudson Parkway, Franklin Delano Roosevelt Drive, the Brooklyn Bridge and the Brooklyn-Battery tunnel.

"The only guy that will have it easy coming into Manhattan that day will be the guy who can walk on water," said Ross, urging New Yorkers to take public transportation and out-of-town tourists to park in the suburbs and take trains into the city.

As for the subway system, which is expected to bear the brunt of the crush, Larry Gould, manager of operations analysis, said it will be running on a rush-hour schedule all weekend, with the ability to handle 500,000 passengers an hour. "We can carry the traffic up to the very highest projections," he said, conceding that "it might be crowded."

Will visitors be shocked by the subway's graffiti and dirt?

"What dirt?" he sniffed. "I've found most tourists like it. They treat it as an experience."

However, the city has produced a special film for the 17,000 sailors expected to descend from the sailing vessels and battleships participating in the festivities. The movie, translated by U.N. personnel into a dozen languages, shows a horror-filled day in the life of an unwary seaman conned by hookers, drug sellers and a crooked cabbie.

A 50-block area of lower Manhattan below Chambers Street and City Hall will be completely closed to traffic July 4-6 for Harbor Festival '86. Dozens of stages will provide free concerts of bluegrass, folk music, gospel music, tap dancing and other entertainment. Four hundred food vendors will offer ethnic specialties, in addition to hot dogs and beer.

Meanwhile, New Yorkers are marking the day in their own ways. A Brooklyn Mercedes-Benz distributor is renting his warehouse rooftops for $100,000 each, while a few blocks away on Montague Street, a cooperative apartment board told its apartment owners that no one could watch fireworks from the roof because liability insurance was unavailable.

The Daily News did its civic duty by reporting that construction workers restoring the statue had been urinating on it, allegedly causing streaks -- a charge the hard hats heatedly denied.

Yachtsman extraordinaire Malcolm Forbes invited former secretary of state Henry A. Kissinger and his wife, Nancy, and entertainer Frank Sinatra to watch the tall ships parade from his 151-foot Highlander, with its personal helicopter. The Chateau Hideaway, a local hotel, changed its name to Liberty Inn.

Tiffany's is advertising a $95, two-inch Statue of Liberty music box that plays "America the Beautiful." Other merchants are offering air fresheners, mattresses and blazer buttons imprinted with Liberty's image.

At the Vista Hotel, whose vistas are of the statue, the bar will be serving "Liberty's Torches," a blend of whiskey, vermouth and lemon juice, and "Americanas" made of bourbon and champagne. But lest welcoming appearances deceive, the hotel has hired security guards to make sure the crowds do not use its bathrooms and telephones.

If all this seems too much, there is always New Jersey. Koch "said come to New York, but New Jersey is really the best place to observe," said Rick Colby of the state's Statue of Liberty Centennial Commission. The 15 miles of waterfront from George Washington Bridge to Sandy Hook offer "spectacular views," he added. (The statue is actually in Jersey City waters.)

New Jersey hoteliers report that the most of the 40,000 rooms within a 30-mile radius of the statue are booked, and Jersey City police are prepared for 500,000 visitors. Eight miles of the New Jersey Turnpike will be closed.

"There's going to be plenty of viewing from the waterfront," said Jersey City spokesman Bob Smith. "It's just a matter of finding a way to get there."

For those who do not want to try, there is another thought. Ross, the city transportation spokesman who has been answering questions for months, said, "I'll be home watching it on TV while I soak in a hot tub."