Since opening in October, the grassroots Grubstake has helped an estimated 150 women, many of them drug-addicted prostitutes who prowled Biscayne Boulevard for tricks, right their upturned lives. Grubstake and its companion thrift store, Good & Funky, are the brainchild of Heather Klinker, who gave up a lucrative job in promotions to launch this venture. Klinker knows whereof she speaks; she's a recovered alcoholic. But among the nonprofits that help the poor, Klinker and her colleagues are anything but impersonal paper-pushers. They help their charges navigate the maze of social service agencies, rehabs, and job placement. They'll give someone a ride to a clinic, or help a woman who is kicking her habit furnish a new apartment with donated furniture. It's the attention to detail that makes her operation stand out. Recently Klinker helped a young addict get a truck out of hock at the impound lot, and brought money to a jailed transvestite so he could buy razors to keep up appearances.