Like the old crack about New York City, it'll be a nice place if they ever finish it. The planet Earth, that is -- "The Living Planet" explored so engrossingly in the 12-part David Attenborough series that continues where his "Life on Earth" left off. In the new expedition, Attenborough shows that there is life on Earth even where by all reason there shouldn't be, and that Earth itself is a living organism, a work in progress.

What a crime it would be, we are meant to think, and do, as the wonders are paraded before us, to interrupt that progress. Bad enough to wipe out the human race, but to bury the yellow-throated martin with it! There's not a moment's preaching in the first part of "The Living Planet" and yet it makes a moving, persuasive visual sermon.

The series premieres Sunday night at 7 on Channel 26 and other public television stations. Attenborough is not the type to stand agape and ogle and tell us what we're seeing is amazing and miraculous, but darned if much of it isn't. This is intrepid television that offers both a wealth of practical information and a rush of astonishing images. Attenborough, the narrator and author, traveled more than 150,000 miles in the three years the series was in production. He proves again a tireless, unpretentious and level-headed guide.

Part 1 is called "The Building of the Earth," and those who pay close attention to what Attenborough says will learn how it is that new land is still being created and why even two miles above sea level there is physical evidence that the sea was once there, too. It seems India is moving a tiny bit north each year and that the Himalayas are actually getting higher. But not to be alarmed. And, honestly, many are the viewers of "The Living Planet" who will probably deduce that even if they don't follow every word of Attenborough's explanations, they can still be pretty thrilled by the whole beautiful thing.

Being not only British but very British indeed, Attenborough is partial to describing circumstances as "very cold indeed," "very high indeed" and "very recent indeed." "Glaciers" are pronounced "glassiers." But there's a remarkably low level of affectation or pomposity in his commentary, which never becomes lecturing. No matter how marvelous the sights are, you don't find yourself wishing he would shut up.

"I've climbed over a thousand feet now," says an increasingly breathless Attenborough as he ascends a Himalaya, passing through forests where musk deer forage and even the vulture achieves a certain nobility. Very few moments later he is in Iceland standing before a raging volcano and noting casually, and apparently without fear for his own safety, that "there are gusts of choking poisonous gas" every now and then.

By no means is this only an animal show, but the animals can't help being prominent -- the snow leopard caught in captivating close-up as it hunts in the brush; the nearly extinct vicun a, a humpless camel that trots gingerly over the Andes in a brilliantly engineered fur coat; huge and seemingly slovenly seals warming their blubber in mud; and a stern snowy owl that bears an uncanny resemblance to Agnes Moorehead.

The best are the penguins, especially in one splendid shot of them bobbing playfully on a small iceberg that pitches in and out of the water. They aren't at all fazed when huge freezing waves crash onto rocks and knock them off. Later, they nimbly amble over ice with baby penguins cradled on their feet. One scene of penguins huddled together while another stands on a plateau looks like a wacky fancy-dress reenactment of the Sermon on the Mount.

Underwater views of polar bears swimming are stunners, but for some reason the camera dwells and dwells on a sequence of polar bears devouring a freshly killed seal. The producers may be boasting about their refusal to flinch from something so bloody. But they overdo it. Like most complaints about "The Living Planet," however, this one is small. The series, produced by Ned Kelly for the BBC and Time-Life Television, and funded by Mobil, is the kind of television at which you can throw words like "glorious" only to have them bounce off as inadequate. If you love the blinking planet you will love "The Living Planet." 'Anatomy of a Controversy'

Comes now the strange case of "Amos 'N Andy," the first TV program with an all-black cast, withdrawn from syndication in 1966 because of what were perceived as offensive racial stereotypes. Something of a movement has developed in recent years to rescue the show from its burial vault and give it circulation again. Producer Michael Avery tries to make the case for revival in "Amos 'N Andy: Anatomy of a Controversy," which Channel 26 will show at 8 tonight and which the Maryland Public Television stations will air Feb. 20.

Although a WETA spokesman insisted yesterday that tonight's is the first local airing for the 1983 documentary, Channel 20 showed it on March 14, 1984. Nevertheless, it merits attention. Despite the fact that some of the show's running gags are repugnant (the lazy janitor Lightnin', expressions like "I'se regusted"), and that it began as a radio program in which two white men played the lead black roles, it also blazed a trail for black comedy on TV, and at least one of its performances, Tim Moore's as George "Kingfish" Stevens, is in the rarefied class of Phil Silvers' Bilko or Jackie Gleason's Ralph Kramden.

"We didn't see it as the epitome of black life; we saw it as comedy," says comedian George Kirby, host of the program. Jesse Jackson, no less, praises those who appeared on the program for having "proved that blacks could act" and for thereby demonstrating "the dynamism of the black mind" during a time when there were few roles for blacks in TV. Alvin Childress, who played Amos, the cab driver -- a totally exemplary character -- also defends the program, and recalls as his favorite scene one from a Christmas show in which Amos explains the meaning of the Lord's Prayer to his daughter.

The late Ernestine Wade, who played Kingfish's wife Sapphire on radio as well as TV, recalls in excerpts from a 1975 NBC interview how she auditioned for the role: "I screamed and I sang and I said, 'I do.' " How attractive she was in her old age. And such performers as Marla Gibbs (of "The Jeffersons") and Redd Foxx credit "Amos 'N Andy" for the ground it broke.

In addition, there are excerpts from the program itself. The print quality is remarkably good, especially compared with the tattered remnants that play repertory movie houses and are available on home videotapes. What stands out is Moore's resplendent Kingfish, the dauntlessly conniving Everyman whose great mission in life was to bamboozle his best friend. Moore's comic delivery is imitated widely to this day, and Carroll O'Connor's Archie Bunker owes something to Kingfish when it comes to malaprop and mangled English: "Hmm, that's bubblin' at a hundred degrees centipede," or "I think I dislocated one of my vertigos."

Now that there is a more widespread, though still insufficient, representation of black life on television, would it be appropriate to revive "Amos 'N Andy"? The case made by "Anatomy" is strong but not conclusive. The program, incidentally, is still owned by CBS. A spokesman for Viacom, which would be the distributor of it were it in distribution, was asked yesterday if there are plans for revival. She checked with a superior. The official word, she said, was, "CBS has it under lock and key." Where, presumably, it will stay.