The Reagan administration promised yesterday to help the fledgling government of Philippine President Corazon Aquino cope with its economic problems, and a senior official said that about $800 million in U.S. and international funds may be available quickly.

Secretary of State George P. Shultz, declaring that "we want to help and we will," said the administration is exploring the Aquino government's needs. The estimate of quickly available aid came from M. Peter McPherson, administrator of the Agency for International Development, in congressional testimony.

White House spokesman Larry Speakes, meanwhile, announced that President Reagan has authorized Secret Service protection for former president Ferdinand Marcos "for a limited time" and that "a planeload of stuff" left behind by the departing Marcos family was flown by U.S. Air Force jets from Manila to Hawaii.

The arrangements for Marcos, who is staying with a party of 90 family members, aides and close friends at Hickam Air Base in Honolulu, appear to fulfill pledges the administration made while seeking to persuade the Philippine leader to surrender power without further bloodshed. Administration officials gave very little information yesterday on the cost or duration of the special arrangements, including housing, transportation and security.

Marcos' former minister of labor, Blas F. Ople, said the Secret Service protection seemed to be the administration's way of honoring a promise that he conveyed Sunday night to Marcos from Shultz that "the United States would facilitate the safety and medical services" of Marcos, his immediate family and close associates if the Philippine leader would step down.

State Department spokesman Charles E. Redman confirmed those promises. He also said that before Marcos left Manila the United States agreed "to transport Marcos, his family and household and their close associates as well as their baggage to the United States and to offer them the opportunity to stay in the United States if they so desire."

Redman said he had no details about how extensive the safety and medical services would be. He said Marcos declined a proffered medical checkup when he arrived at Guam on Tuesday. A military spokesman in Hawaii said Marcos had not requested any medical services there.

Shultz said in an interview on NBC's "Today" show that "obviously he has had some severe illnesses, and undoubtedly good medical attention will be called for and provided."

The military spokesman said Marcos and his party had arrived aboard a U.S. Air Force C141 at midday Wednesday and a second C141 arrived around midnight with baggage and personal effects. At the White House, Speakes said the U.S. Customs Service "will perform a thorough examination of all contents of that aircraft."

An Air Force spokesman in Washington said the cost of taking Marcos and his party from the presidential palace in Manila to Honolulu had not been calculated. Normal operating costs of flying the two Air Force planes from Clark Air Base in the Philippines to Honolulu via Guam totaled about $80,000. No information was available on the cost of the "distinguished visitors' quarters" at Hickam Air Base where Marcos and his wife are staying or the "guest quarters" occupied by other members of their party.

ABC News reported last night that at least $4 million in cash as well as many millions in certificates of deposit and titles to U.S. land were found aboard the two aircraft that landed in Hawaii.

Speakes said earlier that all but about 20 members of the immediate family were given thorough baggage examinations when they arrived in Honolulu and that "customs will perform a thorough exam of all contents" of the baggage plane. Speakes said that anyone bringing in more than $10,000 in cash or negotiable instruments must declare it, but that any amount is permitted as long as it is declared.

Customs Service spokesman Dennis Murphy said last night that agents were still examining the contents of the baggage plane, but that no information would be made public unless a violation of law is found.

The Marcos family is reported to have large holdings in the United States and several other countries. Congressional investigators have reported that Marcos and his wife, Imelda, own at least $350 million in New York real estate.

Shultz said in the televised interview that there is no "exact plan" providing Marcos access to his family's assets in the United States but that the government "will go along" with any "proper and legal steps" that might be taken by the Aquino government. At the same time, Shultz said, "Obviously the things that are his are his."

The House, in a related action, voted overwhelmingly to cite two New York men for contempt of Congress because they refused to answer questions about Marcos' alleged real estate holdings here. Brothers Ralph and Joseph Bernstein appeared last December before a House Foreign Affairs subcommittee.

AID Administrator McPherson told the House Foreign Affairs Committee yesterday that about $400 million, including some appropriated in prior years but unspent, could go quickly to the Philippines. He said the World Bank is nearing approval of $300 million to $400 million in loans.