Is that yellow brick road paved with gold or are all those stones just painted lead?

As "The Wiz" - Hollywood's most expensive musical ever - prepares to open around the country this week, the air is thick with the hype that inevitably precedes anything huge these days.

There is also plenty of advance disaster talk claiming that "The Wiz" is just another budget-bloated film that periodically squeezes, rather than eases, down the road.

But mainly there is sweaty-palmed anxiety for everyone connected with this $20 million (or is it $30 million? or $40 million?) Motown-Universal version of a Broadway musical, which was itself a takeoff on the MGM classic "The Wizard of Oz."

An indication of the apprehension is the fact that MCA Inc. has presold the movie for television, which ordinarily it would not do if it expected a bonanza. Meanwhile, for a musical, the soundtrack of "The Waz" has sold remarkably little advance radio air play, in contrast to "Saturday Night Fever." which had a No. 1 hit by the Bee Gees two months before the picture opened. . . . The box-office difficulty "The Wiz" faces, in the view of those who made it, is that it must score more heavily with black audiences than any other movie targeted for them, and it must also attract huge numbers of whites. "Car Wash," one of the largest all-back movies, grossed $15 million in box-office rentals, against a $2 million investment from Universal. In addition, sales from the soundtrack album paid for the movie, which had a small white crossover audience.

"Yes, I'm very nervous," said Rob Cohen, the producer of "The Wiz." "I'd have to be a saint or a fool not to be nervous. 'The Wiz' is bucking so many Hollywood rules." Such as?

"That a black picture with an allblack cast should not cost over a certain amount of money," Cohen said. "That a large musical is a bad investment because of a limited foreign market, which has become more and more important as movies become more and more expensive. And we also took an American classic and reinterpreted it for the '70s. That's always a chancy thing, when the original work gets enshrined in people's memory.

"All movies are risky. It's only a question of to what degree," said Cohen. "We just pushed it to the Nth degree."

The degree of risk became more apparent this week when both Time and Newsweek strongly panned the picture.

"A huge budget corrupts hugely," proclaimed Time reviewer John Skow. By the end, he added, "the viewer has realized that he can't win, he can't break even, and he must get out of the theater."

Newsweek's Jack Kroll, slightly kinder, said "Director Sidney Lumet's idea to 'urbanize' the story is exactly the right idea, but in carrying out his concept he's produced something that looks very much like white 'liberal' condescension."

It's not a disaster; it's not a disaster," said New York's ace publicist Bobby Zarem, who pulls his thinning hair when things are going well.

Zarem, who engineered last night's charity benefit and has been pumping up expectations for the movie for more than a year with lavish picture spreads in magazines including the debut issue of the revived Life, said that except for the newsweekly magazine reviews "there has been nothing but the most positive talk."

Not exactly. "This is a lemon," said one industry viewer who caught a sneak preview last week. "This movie is going to do four weeks of business, and then it will go out of town. This is another attempt to merchandise hard, and it's arrogant to think that you can redo a classic."

But there have also been some extraordinarily positive reviews, primarily in the Hollywood trade papers.

"Universal can stop worrying," said Daily Variety in its review. "It looks as if they are in the enviable position of having a big, rousing juicy hit on their hands that should enthrall the young in heart (albeit deafening them at the same time)."

And the rival Hollywood Reporter said: "To put it succinctly, 'The Wiz' . . . spells money in the bank for exhibitors."

How expensive is "The Wiz?"

As with most such things in Hollywood, it depends on the accounting.

Although "The Wiz" is officially a Motown production and is only being distributed by Universal, all the money has been put up by Universal, or more accurately, its parent company, MCA.

So far MCA - which is in the midst of a record crop year - has invested $22.8 million, according to the company. MCA claims this figure includes studio overhead. Industry sources say that it does not. Normally, MCA would add 25 percent more, or $5.5 million, for this item. Producer Cohen said, however, there is "a redefined overhead position that is less that 25 percent."

Add $6 million more for advertising to "launch" the movie, with more to come later, plus $1 million more for the initial prints, and it is easy to come up with a cost figure that is closer to $35 million than the $20 million Universal prefers to talk about.

But while MCA has the most at stake, it is also likely to recover its costs before anyone gets a profit participation. As indicated, it has discretion on how much overhead it wants to charge against the picture, and MCA has already made a large number of profitable movies this year including "Animal House" against which they have booked this expense.

"Let's just say [MAC chairman] Lew Wasserman's salary is already covered this year, whether or not 'The Wiz' makes money," said Lee Isgur, an analyst with Paine Webber Mitchell Hutchins, who is one of Wall Street's leading experts on movie finances.

MCA has already presold "The Wiz" to television. This involves what is called a floor presale to CBS. At a minimum, CBS will pay $6 million. In addition, if the movie ends up doing very well at the box office, CBS must further sweeten the pot.

The television rights presale is itself taken as an indication that MCA thinks the movie may be a loser. In addition, MCA has already taken in an estimated $20 million in advance bookings.

What this all adds up to, according to Isgur, is that MCA has largely insured that its own risk is covered, but that those participants who have "points" in the movie, or a percentage of the profit, must wait until the exhibitors and distributors are paid off. "The Wiz" thus must take in about $70 million in gross box-office rentals probably before the participants see a penny above their salaries.

Only two musicals in history have ever done that well - "The Sound of Music' in the 1960s and "Grease" currently.

Meanwhile, there have been some multimilion-dollar musical clinkers like "Star," "Hello Dolly," "Dr. Dolittle," and recently, "Sgt. Pepper's Lonely Hearts Club Band," which was also released by Universal.

None of these has cost as much as "The Wiz."

"MCA knows exactly what its problem is," said Isgur. "They've got a very expensive movie, a movie that has an all-black cast, and for it to be successful at the box office it has to penetrate the black market more than any other film for this market has ever done.

"At the same time," he added, "it has to generate a bigger crossover for white audiences than 'Car Wash.'"

As Producer Cohen put it: "There is an almost apartheid policy in movie theaters. There is a black audience and there is a white audience, and rarely do they mingle in the same theater for the same picture. But when making a movie that's as expensive as this one, we've had to try to appeal to the entire audience.