LOS ANGELES — It’s unlikely that PBS will reinstate Fred Willard as announcer of Market Warriors, its new antiquing reality show, if Los Angeles prosecutors decline to press charges for his July 17 arrest for lewd conduct in a Los Angeles adult theater. The comedic actor, whose role on the show was limited to voiceover announcing, was fired July 19 after news of his arrest went viral. Producers at WGBH tapped Antiques Roadshow’s Mark Walberg to replace him and to re-voice the episodes Willard had already completed. In Market Warriors, which premiered last week, antique-savvy buyers compete to buy and resell collectibles, and earn the highest returns at auction. Because Willard did not appear on screen, no scenes had to be reshot, PBS President Paula Kerger said during her July 21 executive session with the Television Critics Association.