An aspiring artist from the Sunbelt beat out 6,000 other wannabe video jockeys for an instant taste of fame this weekend. Thalia D. DaCosta, 21, of Sunrise, Fla., won MTV’s nationwide search for a VJ on Saturday. Five finalists from around the country were tested on their music knowledge, poise and stamina live on MTV. Viewers voted for the winner over the phone and in cyberspace. “I just won a contest for being myself,” DaCosta said. “I was really a struggling, starving artist yesterday. And today, I have . . . a really well-paying job.” DaCosta, whose first VJ shift starts next week, is taking home $25,000 and a new car. Her salary has not yet been determined.