Imagine George Plimpton. Except with real athletic ability. And he's a woman. And she's taken on a challenge that makes Paper Lion look like a brisk game of Go Fish.   Meet Kathryn Bertine, elite triathlete, former professional figure skater, and starving artist. Just as her personal and professional dreams begin to crumble in the summer of 2006, ESPN stakes her to a dream:  Take two years to make the 2008 summer Olympics in Beijing. As Good As Gold is the heroic, hilarious account of Bertine's serial exertions in the realms of triathlon, modern pentathlon, team handball, track cycling, road cycling, rowing, open water swimming, racewalking, and--fasten your seatbelts--luge.   On her journey, the obstacles range from jet lag to jellyfish, flat tires to floundering relationships, repeated rejection to road rash. But, as time is running out, Bertine doesn't sweat the small stuff, only the large--like scouring the globe for a tiny nation to adopt her, and pushing her body and mind as far as it will go. Maybe all the way to China.   Between harrowing, often laugh-out-loud episodes of triumph and humiliation, Bertine takes short "Water Breaks" to contemplate the ins-and-outs of fan mail, failure, rehydration, nasal reconstruction, and how best to punish steroid users.    Kathryn Bertine swims, runs, and rides--and writes--like a champion. In As Good as Gold, Bertine proves she has something more valuable than an Olympic medal. She's got Olympic mettle. When it comes to the human heart, she takes the gold.