Michele Morgan, an executive assistant at Price Waterhouse in L.A., is asked one question all the time: Are you sure you don't know who the Oscar winners are before their names are read onstage? ''I really don't,'' she says, ''I'll never know.'' Three weeks before the show, Morgan sits at the ''old electric IBM with oversized letters'' that's in her office (''the envelopes are too thick to run through my computer printer,'' she says) and types out the names of the 22 categories on the fronts and back flaps of the official envelopes, which are embossed with a small gold Oscar and lined with red foil so that no one can see what's written inside. Switching to her computer, Morgan, who has had the typing honors for four years, then taps out a separate ''And the Oscar goes to...'' card for each of the nominees. When her work is done, Morgan gives the envelopes and cards to her bosses and chief ballot tabulators, Frank Johnson and Dan Lyle, who do learn the winners' names two or three days before the show. But their lips are sealed.