Mario Biaggi, the New York congressman convicted of corruption charges, is going to prison next month, and his wife of 47 years may not be waiting for him when he gets out. Marie Biaggi filed for a separation earlier this month, according to court records in the Bronx. Mrs. Biaggi, described as a quiet homemaker who shunned the political limelight, loyally stood by her husband as he was indicted, tried and convicted in 1987 of accepting two free vacations and obstruction of justice and then convicted again in the Wedtech scandal. Biaggi is scheduled to report to prison April 10 - 10 days before his 48th wedding anniversary - to start a 30-month sentence.