This time, the powers that be stayed within the institution in choosing a new director for the Congressional Research Service, a vital unit of the Library of Congress that prepares sophisticated and nonpartisan reports for lawmakers. Joseph E. Ross, a 16-year member of the staff, has been named to the post by Librarian of Congress Daniel Boorstin.

Ross' predecessor was former representative Gilbert Gude (R-Md.), whose choice was widely viewed at first as a dip into the political honey pot. But the genial and thoughtful Gude became popular among his subordinates and proved to have clout with his former congressional colleagues. Gude retired Jan. 3 when Ross became acting director.

Ross is a native of Brooklyn, N.Y., and a 1943 graduate of St. John's University. A retired Navy captain (he served chiefly in its legal branch), he was with the Justice Department before joining the research service in 1972 as senior specialist in American law. He progressed through the ranks, once coordinating all research divisions as assistant director. He's a member of the house of delegates of the American Bar Association.

Ross, the father of eight, lives in Annandale. In a voice still mildly tinged with Brooklynese, he said, "I consider myself a Virginian now; I've lived here 25 years." Caen's Bilateral Praise

Herb Caen's column in the San Francisco Chronicle gave generous praise to a State Department employe and a popular former member of the Soviet Embassy staff in Washington who helped return Caen's wandering nephew, John Weymouth, after he walked across the frozen Bering Strait from Alaska to a Siberian island. Caen wrote:

"A lot of concerned and generous people had a hand in this salutary outcome, among them . . . Soviet consul-general Valentin Kamenev in San Francisco , who passed the word to Moscow. Also splendid throughout: Susan Lysyshyn of the State Department's Soviet section in Washington, who put in 48-hour days on this. By the way, she found the Soviets 'totally cooperative.' " Kamenev is a former press counselor to the Soviet Embassy here. Getting Home From Graham

Advertisements for the Billy Graham Crusade suggested that those attending this afternoon's 4 p.m. opener at the Washington Convention Center could get there by Metro subway. Although the subway normally closes at 6 p.m. Sundays, it will stay open, for passengers entering at the Gallery Place and Metro Center stations only, until the session ends. Setting Things Straight

Metro Scene made an arithmetical error in yesterday's column. Gen. Edwin Warfield III, 62, of Baltimore should have been described as 27 years younger than his distant cousin, the Duchess of Windsor, who died Thursday at the age of 89.