SUSSEX COUNTY-The Sussex County Arts & Heritage Council presents its free April First Friday art opening, 5-8 p.m., April 1, at the Gallery in Newton. This month's theme, "Shades of Spring," will feature oils, watercolors, and sculpture. All works are for sale with a 25 percent commission going toward the work of the council. The opening will feature music by the New Jersey Ambassadors of Music in conjunction with the Sussex County Youth Orchestra, which has performed at the Lincoln Center and Carnegie Hall and toured Europe three times. This summer, the New Jersey Ambassadors of Music will embark on a five-concert tour of Europe. For information, call 383-0027; or e-mail firstname.lastname@example.org.