"Good Evening"--the Minnesota Public Radio show designed to replace Garrison Keillor's "Prairie Home Companion"--premiered Saturday to a sold-out house in St. Paul, Minn., and initial reaction was favorable. "It will easily take the place of the old show," said Keillor fan Christine David of St. Paul. "It was terrific!" Host Noah Adams, former co-host of National Public Radio's "All Things Considered," admitted to a few pre-show jitters--"I just wanted to come out here and see if it was as scary as I thought it would be," he told the audience at the beginning of the show. Adams' monologue, titled "St. Croix Notes," received the largest applause.