Peter Hedges' latest, Good As New, will be two-thirds new when Chelsea Altman joins the Off-Broadway cast, March 19. The show was supposed to open Feb. 26 but then delayed a week because star Mercedes Ruehl bowed out because of a television commitment. Laura Esterman stepped into the lead role, playing alongside John Spencer and Jennifer Dundas.

Now the show, which has received mostly positive notices, is extending -- to April 6 -- but Dundas must leave the cast to go into Lincoln Center's Little Foxes, hence the Altman switch. Altman was featured in The Monogamist at Playwrights Horizons (Nov. 1995). The actress will play 16 year-old Maggie, who confronts her mother (Esterman) about mom's new face.

The show was first supposed to close March 9. Then, with the change in opening date on Esterman's arrival, the closing date was moved to March 16.

Spencer is best known for playing Tommy Mullaney on TV's "L.A. Law." Esterman, a Drama Desk, Outer Critics Circle and Obie winner for Marvin's Room, appeared on Broadway in The Show-Off, Metamorphosis, God's Favorite and The Suicide.

Peter Hedges' previous plays include Imagining Brad, Oregon and Champions Of The Average Joe. His novel, What's Eating Gilbert Grape, was adapted into a feature film. David Van Tieghem provides original music for Good As New, which will have sets by Rob Odorisio, costumes by Sharon Sprague and lighting by Blake Burba. Now in its 11th season, Manhattan Class Company has produced such works as Nixon's Nixon; Three In The Back, Two In The Head; The Grey Zone and A Snake In The Vein.

For tickets ($25-$30) to Hedges' tale of "a nuclear family discovering love may still be possible even after you tell the truth," call (212) 727-7765.

--By David Lefkowitz