The vast wealth of Howard Hughes, whose bizarre life has spawned an estate battle almost as unusual, finally moves toward distribution Monday with a scheduled trial in Las Vegas on the authenticity of the so-called Mormon will.

Seven days later, a trail is scheduled here on whether the state of Texas can collect inheritance taxes on Hughes' legacy - a crucial scene in one conceivable legal nightmare in which state and federal inheritance taxes could consume all of the estate.

Already the battles over the distribution of Hughes' wealth, estimated variously at $168 million to $1.2 billion - have see at least $1.4 million in legal fees awarded from the estate, with hundreds of thousands of dollars more awaiting court approval, under appeal, or yet to be incurred.

In addition are the conflict over the "Mormon will" - in which Hughes purported by left one-sixteenth of his estate to a penniless Utah gas station attendant - and the question of whether Texas was his legal residence at death. Gag orders have been imposed on lawyers for both sides in each case.

All told, it is an appropriate untying of the Gordian life of Hughes, whose name for years was a national symbol for mysterious wealth.

The old man died on April 5, 1976, at 70 while fying from Mexico to Houston for emergency medical treatment. He has since been portrayed as a frail man whose last years were spent in seclusion and drug-induced confusion while aides maneuvered for power.

The "Mormon will" at issue in court this week was found in the Mormon church headquarters in Salt Lake City shortly after Hughes' death. It called for one-fourth of the estate to be distributed to the Howard Hughes Medical Institute, one-eight to four universities, and a series of one-sixteenth shares to individuals, scholarship funds, the Mormon church and sometone named "Melvin."

Melvin Du Mar proved to be a Willard, Utah, gas station. He said he believed he was in the will because in 1968 he had helped a man identifying himself as hughes, whom he said he found hurt and lying in a ditch near Las Vegas.

Attorneys challenging the will say they have evidence it is a forgery and was not handwritten by Hughes. Du Mar's thumb print, they allege, was on the envelope, and Du Mar has reportedly told lawyers he delivered the will to the church headquarters.

The alleged will names former Hughes associate Noah Dietrich as executor of the estate, 50 Dietrich's attorneys in the Las Vegas trial will try to prove that the document is genuine.An executor's fees are paid from the estate.

An aunt and cousins of Hughes are challenging the will; if it is found to be ersatz, the relatives stand to inherit what is left of the Hughes estate after taxes.

And taxes are central to the Houston trial. Texas Attorney General John Hill says that whatever Hughes' journeys, hotel accommodations and business dealings elsewhere, his last legal domicile was Houston. His draft registration, business banking, federal tax returns and his fountainhead business, Hughes Tool Co., all were located here or carried Houston addresses.

Texas' 16 per cent inheritance tax, then, would bring the state anywhere from $30 million to $200 million, depending on the eventual value of the estate. The 16 per cent would be credited against federal estate taxes which would be 77 per cent; so Texas would get 16 and the U.S. government 61 per cent.

Nevada has no inheritance tax, and so attorneys for the Hughes relatives are trying to prove that his last legal domicile was Nevada. He owned propoerty there, lived at the Dessert Inn in Las Vegas, ran his Summa Corp. holding company there and it was the last place Hughes had been in the United States before his death. Thus if the estate is probated in Nevada, the U.S. government would get 77 per cent.

But California officials are expected to try to collect taxes in their state because of hughes's activities there. California has a 24 per cent inheritance tax. Since the federal government allows no more than a 6 per cent credit against its taxes the heirs thus could face inheritance taxes, if both California and Texas are permitted to levy them, of 61 per cent federal, 16 per cent Texas and 24 per cent California - 101 per cent of the estate.