The Louvre closed Monday for five weeks while workers put finishing touches on the first phase of an $850-million expansion project to be inaugurated March 30. The Grand Louvre, as the renovation project is known, will nearly double the Paris museum's exhibition space by 1995. Changes include a 70-foot glass entry pyramid soaring out of a courtyard and leading to a vast underground lobby containing ticket windows, shops, restaurants, libraries, temporary exhibition spaces and an auditorium. New electronic panels giving directions and other information on museum activities will also be installed to reduce confusion experienced by past visitors (3.5 million last year) to the museum's 250 exhibition rooms. Ticket prices will increase from about $3.30 to about $4.15. This is the first time the museum has closed in nearly 200 years.