Though he has limited skills and performs his job adequately at best, the single most replaceable person at Lucas Research Associates announced Monday that he will resign immediately if he does not receive the salary increase he has demanded. I walked into [department supervisor Eric] Shaws office and told him I get a 10 percent raise or Im out of here, said Stanley Morgenstern, 37, who according to company sources holds a position that would immediately draw hundreds of equally qualified applicants were it to become vacant. I am not bluffing. If they say no, thats itIm gone. At press time, reports confirmed that negotiations had ended with Morgenstern agreeing to stay on for two weeks in order to train his replacement. 