Palestinian guerrilla leaders were jubilant today over the resignation of Secretary of State Alexander M. Haig Jr. and what they regarded as a major diplomatic victory in staving off a final Israeli onslaught of their camps in West Beirut.

Smiling and defiant, Palestine Liberation Organization leader Yasser Arafat and his top aide Salah Kahalaf, also known as Abu Iyad, inspected the extensive damage done by Israeli shells and rockets during the past two days in the Palestinian district of Fakhani in the southern outskirts of the city.

"American civilization. American human rights. Here we are," shouted Arafat, pointing to the debris of a building hit yesterday by rockets fired from Israeli jets.

In a later statement, Arafat said, "The Palestinian and Lebanese nationalist guns will never be surrendered to [U.S. envoy] Philip Habib."

At the offices of the PLO Information Department, Palestinian officials chatted amiably with Western reporters as if they had just emerged victorious from a major battle. Seemingly they were indifferent to the massive arsenal of Israeli weapons trained upon them from the nearby mountains.

Mahmud Labadi, the official PLO spokesman, joked about a piece of shattered glass that had hit him when a rocket exploded.

The mood of victory was also reflected in a PLO statement that said, "Yesterday the PLO was asked to surrender unconditionally by Alexander Haig via at least two channels against a background of increasing Israeli attacks. This morning, Alexander Haig has resigned his post and the PLO still stands with its head unbowed."

The PLO cockiness is something American and Lebanese mediators will have to deal with now that the cease-fire has taken effect here, apparently as a result of Haig's resignation.

Habib and Lebanese President Elias Sarkis were continuing to hold meetings today with various Lebanese mediators to discuss terms for an "honorable surrender" of the 5,000 to 6,000 guerrillas trapped in West Beirut.

The PLO leaders, at least outwardly, seemed unwilling to talk of surrender today, at least on American or Israeli terms.

One official noted that none of the plans Palestinians have proposed, even the French one they helped to draft, calls for their disarmament as the Israelis and Americans are demanding.

"A full disarmament is not possible until we go to Palestine," remarked the official. He also rejected a stockpiling of the guerrillas' heavy weapons in their camps and said only "some limitations" on their arms was acceptable.

"In none of our plans is anyone turning in arms to anybody," he said.

The latest PLO plan, which Lebanese Prime Minister Shafiq Wazzan gave to Habib yesterday, calls for guerrillas to return to their camps only after the Israelis begin a withdrawal of their forces and the Lebanese Army, the United Nations or other international observers come in to act as a buffer between the warring forces.

Following this disengagement of forces, the PLO would order its guerrillas to return to the camps and begin negotiations with the Lebanese authorities on the question of a future armed Palestinian presence.

This presence, local press reports said today, would consist of a formal military body, like a brigade the Palestinians have under Syrian Army command, that would presumably be placed under Lebanese authority.

The PLO would also keep its diplomatic status and various political, economic and cultural offices in Beirut, and the Lebanese government would recognize the civil rights of the 500,000 Palestinians living here.

The PLO, in turn, would give full recognition to Lebanese authority everywhere in the country, doing away with Palestinian-run zones.

Nowhere in the plan is there any suggestion that the PLO leaders would leave Beirut to be based in another country.

Thus, the PLO seemed to be still holding out for both a srong military and political presence in Lebanon, a condition Israeli and American officials, at least until the resignation of Haig, were rejecting as unacceptable.

There was more reason for Palestinian optimism than a tenuous cease-fire and Haig's departure.

PLO officials noted that the Palestinians now have gained the strong diplomatic backing of the Soviet Union, France and above all, Saudi Arabia, which they reported was using all its influence to press the Reagan administration to force Israel to halt its invasion and stop threatening to attack the capital.

One PLO source said the Saudis have gone so far as to warn Washington that they would seriously consider an oil boycott, withdrawing Saudi investments in the United States and establishing diplomatic relations with Moscow if Israel entered West Beirut to crush the Palestinians. These reported Saudi threats could not be confirmed with other sources here today.

Western diplomats and Lebanese leaders showed concern that the resurgence of Palestinian confidence could become a real obstacle to a negotiated solution and might lead to another round of fighting that would end with an Israeli assault on West Beirut.

"The PLO have to realize the game is over," said one diplomat. "Militarily, the game is over. Politically it can rise again. It really depends upon whether the PLO will be responsible or not. They have to remember the Israelis are holding an awful lot of cards."

Saeb Salam, a former Lebanese prime minister who has been playing a key role in contacts between the United States and Arafat, said the PLO leader "cannot consider himself finished or crushed under the invader" after the cease-fire and Haig's resignation.

Nonetheless, the situation demands "more wisdom" now from Arafat, he said, adding that he hopes the Palestinian leader does not overplay his hand and harden his position.

"Our problem is dealing between the euphoria of the Palestinians and the disappointment of the Christians," he said, referring to the hopes of Bashir Gemayel's Lebanese forces that the Palestinians would be crushed by the Israelis.

It is precisely "this euphoria" that now looms as a major new obstacle for Habib in his effort to arrange what he reportedly has called an "honorable solution" and that Salam insists must be "an honorable surrender."