WHAT WOULD it be like to scour the world for the finest of everything, to employ the top experts in every field, and to bring the treasures thus selected home for your living room? How does it feel to live in a 77-room house attended by 14 live-in servants (not counting platoons of extras where needed)?

Get yourself over to Wilmington, Del., before the end of November to visit Nemours, the private residence of the late Alfred I. du Pont, and you'll come close to knowing.

Nobody cay say what everything cost; du Pont carefully destroyed all records as he went along. But it's safe to assume there can hardly be many mansions equal to it in this country. The iron gates to the garden were forged in 1488, a gift of Henry VII to Catherine Parr -- Kate's gate, as du Pont called it, "keeps the cows out of the garden." The clock in the downstairs room, which plays an 18th-century air on the hour on its 19-pipe organ, was made for Marie Antoinette. One of the beautiful chandeliers once hung in Lafayette's house.

But his is not a museum, it's a home. The splendor is matchless, but it is alleviated by remaining touches of the man who owned it. Occasionally you get a peek into the lives of Alfred and his bride, Jessie, and it all becomes twice as interesting.

For one thing, we learn that he was a stickler for perfect maintenance. He toured the boiler and heating rooms (surely the Taj Mahal of the genre) daily. While he was alive the statuary in the garden was wsahed down once a day and servants assiduously picked the dark stones from the light in the gravel paths. He wanted things perfect and he was imaginative about it. When Jessie gazed on the closest of her gardens from her bedroom window, her view was foreshortened. The gardener had received instructions to enlarge the north end.

In his will, du Pont ordered the mansion opened to the public after the death of his wife. He died in 1933 and she is 1977, and after he was gone she turned her attention more and more to her charities and less and less to the maintenance of Nemours. When upholstery wore out, she ordered a replacement from whatever was in the attic. Maintenance of the ground shrank to the area she could see from her window. The maze garden, the sunken gardens, the rock garden, the reflecting pool and the Temple of Love with the Houdon, all paled beside her philanthropic work. Since her death, the restoration project has lovingly reproduced the original splendor, painstakingly matching original colors, ordering duplicate laces and patterns.

The guides who take tourist through in groups of no more than six will not mention this, but if you look at the top of the 10-foot stone walls surronding the 300-acre estate, you'll see the broken glass set in cement Alfred du Pont had put there to thwart uninvited guests. There are some who say the people he wanted to keep out were his own relatives. Toward the end of his career, three relatives banded together to take control of the famous du Pont de Nemours Company from him, and things were never the same afterwards.

Tourist arrive at Nemours on a special estate bus and disembark at the rear terrace where they are offerred a glass of orange juice and a rose proffered on a silver tray. The famous tulip poplars, visible from the terrace, are the same that the young Alfred often stopped under to rest enroute to the market with his father. In the shade of their branches, his father repeatedly remarked that, if he were rich, he'd sit all day on the veranda of his house, reading and eating ice cream. The mansion was laid out in 1909 with care not to disturb these poplars and, in the basement of this grandLouis XVI chateau designed by Carrere and Hastings of New York, is an ice cream plant.

The gold trim on the stair railings is 23-karat, the Persian hunting rung's only equal in this country is in the Metropolitan Museum, yet there are nice domestic touches. On the wall of a daughter's bedroom is her certificate of excellence for elementary swimming and "resuscitation of the apparently drowned." In the basement exercise room is an ancient forerunner of the steam chamber equipped with electric bulbs that once dealt a thrid-degree burn to a guest hoping to shed a few pounds. On the wall below the stairs, among the Prussian battle helmets and battle taxes, is a 31-pound stripped bass hooked by Jessie du Pont. the small touches seem to balance the granleur and keep the scale human.

Nemours' admission is $4 and reservations are advised.

If you visit Nemours during October, it is possible you can combine the trip with the fall foliage run of the Wilmington and Western Steam Railroad, departing from Greenbank, near Price's Corner. At the writing, the date was not final, but you can call (302) 654-4630, home phone of Peter Steele, one of the directors, to get the date. If that particular weekend in October you can bring a picnic and take a mile-and-a-half ride behind an old fashioned steam engine to Marshalton along the Red Clay Valley.

The fall foliage trip is an all-day affair, with photo stops along the way. You can ride in open cars, sitting on antique church pews behind a 330-ton Royal Hudson from Canada, and you'll turn round for home at South Modina, Pa. This is one of the high spots of the year for steam engine buffs, and about 500 are expected to show up.

If you're not picnicking, the Columbus Inn, which was once host to Buffalo Bill, Sitting Bull and Annie Oakley and is still doing business in Wilmington, is attractive for lunch. The inn's two open fireplaces are popular in the fall, and the scallops I ate here -- Narragansett Bay scallops that the inn thinks are the best -- linger in my memory.

The pedestrian mall in downtown Wilmington is built around a group of restored 18th-century houses. Across the square is the beautiful old Town Hall built in 1989, now a museum, and is worth stopping at to see the displays relating to the early history of Delaware. The painted wooden statue of George Washington just inside the door replaced the one of George III in New York city after the Revolution, but fell on bad times and ultimately had to be rescued from an ignominous post outside a cigar store. It was carved in 1792 and is scheduled for loan to our Smithsonian this winter.

Farther down the mall is the Bank of Delaware, making its mark in this century because the Hunt brothers stored their silver here. And just beyond is a charming old survivor of another age, the Grand Opera House, a registered National Historic Place whose cast-iron facade in the mid-Victorian Second Empire style has just recently been rescued in the nick of time from the wrecker's ball.

The Grand's were trod by the likes of Edwin Booth, Maude Adams, Ethel Barrymore and George M. Cohan. Buffalo Bill Cody's Wild West show made several appearanes here. Adm. Robert Perry, returning from the Arctic; recounted his adventures at the Grand. But times change, and by 1971 its seats were empty and part of its iron facade had been torn awa for store fronts, leaving it for demolition. Citizen protests saved the Grand and today it is back in business, renovated, restored and packing them in with live entertainment from opera to puppet shows. If you're spending the weekend in Wilmington, an evening at the Grand could be fun.

With a population of only 70,000, you might not expect Wilmington to have a four-star hotel, but its elegant Hotel Dupont, reminiscent of New York's Plaza in the old days, earned the high rating from the Mobil Guide. Its $12.50 Sunday brunch is so famous that reservations are a must three to four days ahead of time.

Brunch in the Green Room is a Wilmington tradition, with two chefs making eggs and pancakes to order and an elegant table dominated by carved ice sculpture. The service in the Dupont is faultless and augmented by extra touches that make a difference. Towels are changed twice daily, beds are turned down and a chocolate is put on the bedside table; coffee, a croisssant and a newspaper are delivered to your room in the morning and, if you prefer a real beakfast downstairs, the orange juice is freshly squeezed. The Dupont, in business since 1913, takes its four-star reputation seriously and the rooms are being luxuriously redecorated and enlarged.

Dinner in the Brndywine-Christina Room is served under the hotelhs extensive collection of Wyeth paintings. The restaurant is bucking for four-stars to match its parent hotel and offers good food with flawless service.

The best thing about the Dupont, however, are the weekend bargains. The double rooms are $83.50 to $93 during the week and drop to $59.50 weekends. The Brandywine Overnight package for two for one night is $56 per person, and throws in a $50 certificate toward dinner downstairs and also pays the 6-percent state tax. Stretch your stay to two nights on the package and you get Sunday brunch instead of the $5 allowance for dinner, while the cost is $69 per person.