A one and a two, it's “Polka Time” at the mammoth ballroom in Gibbon, Minn., where some lively aficionados describe their love of this “happy music.” Most of them are getting on in years. (One young musician notes, “The women are all 80.” Well, not quite.) And the ballroom's future is in doubt, co-owner Steve Seeboth concedes. But 74-year-old Wally Pikal, whose specialty is playing two trumpets at once, insists he “ain't quittin'.” And dancer John Wirtz, a retired Coast Guard officer, says, “I just love the exhilaration.”