THE Wharton School has unveiled plans for its high-tech, 300,000-square-foot academic center, scheduled to open in 2002 on the site of the old Penn Bookstore. Designed by Kohn Pedersen Fox Associates, the $120-million center has entrances on Walnut Street and Locust Walk, and is being funded entirely by Wharton alumni contributions. A groundbreaking ceremony will be held in April.