It was Palm Sunday and Joe Del Po looked pleasantly bewildered in the glare of TV lights. He cradled his trophy, a symbol of the $25,000 the Rockville lumberyard owner had just won by finishing second in the finals of the world's richest craps championship.

Del Po, a 44-year-old bridge and rummy player, entered the tournament at the Resorts International casino along the Atlantic City boardwalk on a lark at the urging of friends. "Really, I just came up for the ride," said Del Po, whose son, Joe, and daughter, Lori, watched in the crowd. "I never thought I'd get this far. I really don't know the game. It'll probably hit me later."

But now, Del Po was sipping champagne and being congratulated by tournament cohost Johnny Unitas, the former Baltimore Colts quarterback, who spoke over the tambourine-like din of hundreds of slot machines.

A much larger throng gathered inside the red-rug-and-mirrored-wall casino. The gamblers scarcely paused from wringing their hands at the blackjack tables, gyrating under the roulette wheel, or muttering at the pairs of red dice hurled across dozens of other craps tables.

The 36 semifinalists who fought out the championship today were the lucky high rollers. Luckiest of all was the champion, a 29-year-old salesman from New Jersey named David Warling, who won $75,000. The average gambler at the Resorts International casino loses $18 an hour and contributes in his own way to the average $500,000 a day that the casino takes in.

'Day' is a misnomer. Sunday morning in the casino was merely an extension of Saturday night. Outside, the beaches that made Atlantic City famous were deserted and a stiff wind swirled sand along Danny Thomas Avenue.

Inside, thanks to the tournament and Frank Sinatra's weekend appearances, the casino was crowded even when it opened at 10 a.m., following a four-hour cleaning and money-counting hiatus. Cocktail waitresses, whose outfits give new meaning to 'scantily clad,' served coffee and doughnuts to players.

Bank craps, as the popular dice game is called when played in a casino, has come a long way since prehistoric man rolled six-sided sheep ankle bones. The shooters, as players are called, crowd around an oversized felt-covered table that looks like a cross between a sideboard and a large coffin. In the middle, the "stickman" shepherds the dice about with a modified crook, announces bets and watches for sleight-of-hand funny business.

On the "house side," two dealers lay down players' bets. Between them sits the "boxman" who supervises the outflow of chips (or checks, as they are known) and the influx of dollars, which he stuffs into a drop box under the table.

The shooters arriving for the midday elimination round came from as far as Wyoming. They were an unpretentious bunch, all men and mostly middle-aged. Numbered among them were iron workers, contractors, shot blasters, salesmen, a tailor, a pharmacist and a chef. Each entrant paid a fee of $250 and risked $750. Those who won at their tables went on to the next round.

"These guys, if they win $75,000 that's only a tenth of what they lost," said Joe DiSalvo, whose father was a semifinalist. "Ask them how many cars they've hocked, how many houses they've mortgaged. Just one big score--that's what everybody dreams of."

The best show was James Cool, a curly-haired iron worker from York, Pa., who brought his three lucky hundred-dollar bills, chewed Chiclets with vehemence and called out to Jesus with every crucial roll. But the Lord works in mysterious ways and Cool, who said he had been playing craps since "six months before I was born," made it to the finals but finished fifth.

Norman Williams, an ice cream wholesaler from Hyattsville and a bass player who once backed up Lester Young and Billie Holiday, dreamed of a big score, but was the first semifinalist eliminated.

Superstitious like many gamblers, Willy Williams blamed his sorry showing on his shoes, which he said he had neglected to have shined. He donned the same maroon shirt, blue blazer, gray pants and undershirt he wore during his first two victories. "The last thing my partner said was to get my shoes shined," Williams said. "I forgot."

Williams says he can't remember a time when he didn't play craps. He threw the dice growing up in Washington, in the Army, traveling with jazz bands in between gigs with Liberace and later with Woody Herman ("Talk about extremes!"), he said. And during the winter when the ice cream business was slow.

"It's a game where you can become instant friends with someone," he said. "It is camaraderie. I've never gambled the rent, and I expect to lose, but I enjoy myself even when I lose." Gambling has even helped Williams survive two heart attacks. "Some doctors claim it's just as good for the coronary arteries as jogging. In the early rounds there was one old gentlemen who had his nitroglycerine on the rail. You're not allowed to put your hands in your pockets and I asked him, 'If worst comes to worst, can I borrow it?'"

Playing at table three next to a sign that advised any publicity-wary contestants that photographers and TV cameras would be taking pictures, Williams lost his bid for the championship on one $400 roll.

At the end, keyed up and drawing on a cigarette, Williams held the dice for 10 rolls before he "sevened-out." The "pit boss" promptly showed him out, saying, "Mr. Williams, thank you very much. I hope you had a good time."

On the floor of a casino, bankruptcy is worse than leprosy and fame is fleeting. A minute after his loss Williams approached one of the tournament's organizers for some extra brochures. "Remember me?" he asked.

In the finals, Joe Del Po stood impassively at the end of the craps table mastering his emotions except for a few quietly clinched fists and can-you-believe-this glances to his son and daughter.

His one concession to superstition had been to enter the casino by the same door he had taken the week before. "You hate to go against the fates," he said. "C'mon, Dad," Lori said, rubbing her hands together.

The championship round was a game of attrition to see who could lose the fewest chips. Del Po started with $750 and ended with $781. The winner edged him by $99, a slight margin that was worth $50,000. Posing before the cameras, the winner smiled maniacally, grasping piles of cash. CAPTION: Picture 1, Joe Del Po awaits counseling of the chips after winning second, and $25,000 in craps championship. AP; Picture 2, Finalists compete for $75,000 top prize in craps championship.