A man who said he would replace the Forsyte Sage on TV here Sunday nights did the next best thing Tuesday in Milwaukee - boosted beer. Author Jean Shepherd, 42, (he writes for Playboy but says he never finds anyone who admits to reading the magazine), was guest of honor at a beer garden party at the Pabst Brewing Co. He and Fred Barzyk, 33, a former Milwaukeean, are in town with their crew in connection with production of a new PubIic Broadcasting System television series, "Jean Shepherd's America." The 13 week series of half hour shows, filmed all across the country, will be seen 8 p.m. Sundays on Channel 10 starting next April. Milwaukee will appear in three segments. Barzyk, once active with the Marquette University players, is producer. He is the som of Mr. and Mrs. Stanley Barzyk, 2814 W. Vogel Ave. Greenfield. Shepherd, who has appeared on radio and TV, will narrate the show. Amid the raor of beer trucks proceeding up the W. Juneau Ave. hill, Shepherd narrated the following: - He has been around the globe three times and beer - not sex - is the universal language. - One show will celebrate beer. A 10 foot high mosaic of beer labels will appear and three minutes of beer ads will he heard. With a blast of Beethoven, a view down a big vat will be shown. Then Shepherd will announce, "To truly appreciate tonight's show, we'll give you 10 seconds to get a beer." - Filming Tuesday in Milwaukee included a beauty shop where women bring their own beer to pour on their heads (as a rinse). By Wednesday night the crew will be in Alaska, Shepherd said. (Arrival here was Sunday.)