KCBS-TV Channel 2 will host "Earthfest '98," billed as Southern California's largest Earth Day event in 20 years, on Sunday at the Santa Monica Pier. Co-hosted by Heal the Bay, the 11 a.m. to 7 p.m. event aims to educate families about how to help clean up their communities and nearby oceans. . . . UCLA Center for the Performing Arts has added a second show for KCRW-FM's (89.9) "Joe Frank: In Performance," on May 1 at 11 p.m. at Veterans Wadsworth Theater. The spoken-word artist's 8 p.m. performance that night is sold out. . . . Bill Cosby will deliver the commencement address and receive an honorary doctorate at USC's 1998 graduation ceremony on May 8. . . . Director Ron Howard will be honored as "a consummate filmmaker and an outstanding citizen of the filmmaking community" when he receives the Society of Operating Cameramen's 1998 Board of Governors' Award on April 26 at the Ritz-Carlton Hotel in Marina del Rey. Previous recipients include Steven Spielberg, Kathleen Kennedy and Jacques Cousteau. . . . Two of this year's comeback actors, Burt Reynolds ("Boogie Nights") and Sylvester Stallone ("Copland"), are being honored at the Palm Beach International Film Festival in Florida. Stallone was to have received the Lifetime Achievement Award Friday night, and Reynolds will receive the Film Excellence Award on April 25. . . . Speaking of Reynolds, lawyers in his Florida bankruptcy case are again haggling over his earning power now that it has been increased by his Oscar nomination this year. A judge this week ordered attorneys to redo a reorganization plan for creditors' approval. Reynolds' lawyers project he'll make $150,000 a month for the next two years, but attorneys for the creditors--to whom Reynolds owes $10 million--believe that the estimate should be higher.