Five days after President Reagan made a personal appeal for a donor, 16-month-old Candice (Candy) Thomas of Accokeek, Md., has a new liver, following a 10-hour operation at Children's Hospital here.

Dr. Jeffrey Malatack, one of three physicians in charge of post-operative care of the hospital's famed liver transplant unit, said late today that Candy came through the delicate surgery "in better shape" than the typical child transplant recipient.

President Reagan talked to Candy's parents, Stewart and Penny Thomas, for three or four minutes at about 10:30 a.m., "to see how things were doing, and to send his best wishes to the family and child," according to White House spokesman C. Anson Franklin.

Stewart Thomas, 36, praised the president because he "opened the door for us and for families like us" in his nationwide radio address last Saturday, in which Reagan appealed for donors for Candy and two other children.

Penny Thomas, 32, said her blond-haired, blue-eyed daughter was awake and alert, "but not smiling," late this afternoon. She said she was worried because Candy was running a high fever.

Hospital spokesman Dick Riebling said Candy was listed in critical but stable condition, which he said is normal following transplant surgery.

"She's doing as well as anyone can expect," added Dr. Malatack, who said doctors must watch closely for signs of infection or rejection of the new liver for several days after surgery. "We haven't seen any signs yet," he said. "Every day that passes increases her chances of survival."

Candy's ailment, biliary atresia, accounts for about 40 percent of all liver transplants, according to Dr. Malatack. He said the congenital condition results in unformed bile ducts that never grow to functioning size.

Penny Thomas said the president first became interested in Candy's plight after Channel 9 broadcast a story about her last December. She said someone from the White House called their house in Prince George's County and offered to provide an Air Force jet to fly Candy to Pittsburgh once a donor was located.

In the meantime, the Thomases made private arrangements for a plane to bring them here when a donor was located. But Penny Thomas said "when they the hospital called me, I couldn't find the number for the private arrangements we had made. Then I remembered what the president said he repeated the pledge in his radio broadcast last week , and I called the White House." The family went to Andrews Air Force Base in an ambulance Wednesday afternoon and then flew to Pittsburgh.

The all-night surgery, performed by a team headed by Dr. Thomas Starzl, the hospital's transplant pioneer, began at 8:15 p.m. Wednesday and ended at 6:30 a.m. today. Starzl and other members of his team flew to Denver Wednesday morning, in a jet donated by U.S. Steel, to remove the liver from a brain-dead child there. Before flying to Denver, Starzl and his team transplanted a liver from a drowning victim to Clayton Conger, 4, of Rock Springs, Wyo. Like Candy, Clayton was listed in critical but stable condition today.

The Associated Press reported that two other liver transplants had been performed since Wednesday. In Minneapolis, doctors at the University of Minnesota transplanted a liver into 8-month-old Koren Sharie Crosland of Fresno, Calif. An Air Force jet flew a liver from Salt Lake City to Memphis today, for transplant recipient Louis Ragsdale, 8, of Memphis.

Hospital spokesman Riebling said the cost of the surgery and related care ranges between $70,000 and $150,000, and that because the procedure is still considered experimental, some states and insurance companies cover the costs and others don't.

The Thomases said they are covered by Blue Cross-Blue Shield but that it had not been determined if any part of Candy's medical bill would be covered. Hundreds of neighbors in their rural area south of Washington have raised $76,000 since last September, in anticipation of today's operation.

"We'll have to continue raising money now more so than ever because the bills are going to start rolling in," said Hilton Conley, treasurer of the Accokeek Volunteer Fire Department, which coordinated the fund-raising.

Stewart Thomas an electrician employed by the federal government's General Services Administration, has been assigned, at his request, to the White House for the past month, but will work temporarily at a federal building here during Candy's recovery period.

Candy's father made arrangements for his assignment here after doctors determined that she was a candidate for transplant surgery.

The Thomases, whose other children, ages 13, 8 and 4, are staying with relatives at their home in Accokeek, spent a restless Wednesday night in a lounge at the hospital here. They said they plan to seek temporary housing here, for a recovery that could last from two to five months.