VENICE -- Before leaving Washington for this elegant and ancient city, White House chief of staff Howard H. Baker Jr. called ahead and asked his deputy, Kenneth M. Duberstein, if he needed anything from home.

Duberstein, who grew up in Brooklyn and is fond of hot pastrami sandwiches as well as other such American delicacies, said there was just one thing: could Baker bring some "American" coffee? Duberstein said he and Communications Director Tom Griscom couldn't drink the strong, viscous espresso they found here.

Baker didn't let them down. On his way to Andrews Air Force Base to fly in the president's back-up plane to Venice, the chief of staff stopped his White House car at the 7-Eleven store in Morningside, just outside the base. As the story is being told here, Baker then prowled the shelves for a few jars of instant coffee to satisfy his top deputies.

He was also eyeing the Twinkies on the pastry shelf when his assistant, John Tuck, tugged him away. Duberstein and Griscom, who had accompanied the president on the first leg of his trip here, were glad to see Baker arrive -- and get their precious cargo. EACH NATION participating in the economic summit sends an official representative known as a "sherpa," who makes preparations for the summit. On her arrival the other day, the Canadian staffer, Silvia Ostry, suffered the kind of misfortune that sure-footed sherpas are supposed to avoid whether they find themselves in the Himalayas or Venice -- she accidentally fell into a canal at the airport. AT A TIME when they are incurring sharp budget cutbacks because of takeover threats and harsh competition from cable outlets, the American television networks have made elaborate preparations to cover the summit. Network officials say the Venice coverage will cost their organizations more than $1 million each.

Dozens of camera crews have been scouring the city for scenic shots of famous landmarks and tourists to leaven the serious news of the summit. A whole armada of speedy water taxis have been hired by the networks to ferry tapes and employes around the city. THE NETWORKS HAVE also gone to great lengths to provide interesting backdrops for their evening news broadcasts, which occur after midnight Venice time. NBC, for example, installed klieg lights to illuminate a church directly across the Grand Canal from the Bauer Grunwald Hotel, where a makeshift set for anchorman Tom Brokaw and others has been placed on the roof.

Cable News Network has also made its mark. In the press centers and even in the offices of the traveling White House the monitors were tuned to CNN, which was carrying live coverage of the Iran-contra hearings.

Even as the White House sought to showcase President Reagan as a statesman on the world stage, the Iran-contra affair reverberated in Venice. Some White House officials were not all that happy with the demands by Secretary of State George P. Shultz that Assistant Secretary Elliott Abrams remain on the job despite his admissions of misleading Congress about the secret contra resupply missions.

Said one official: "We'd gladly trade Elliott for $75 million in contra aid."

Baker was asked today in an interview on "Face the Nation" if the president would still keep Abrams on board should Congress balk at renewing contra aid.

"Well, you don't authorize human sacrifice lightly," Baker said. "And, you know, that's sort of what you're talking about."

Reagan, he said, "is not mad about throwing people to the wolves" and still supports Abrams. The president, he added, "has not been told by Congress that you've got to build a bonfire and burn Elliott Abrams in exchange for $300 million for Central America, and I hope it doesn't come to that."