The amount of work it takes to replace one you will be better off buying a new one with a warranty. I got mine from oreilly's for $40. I think rock auto had them for 32 plus shipping.
Part # is 42-19
fits these vehicles
BUICK(1979 - 1993)CADILLAC(1979 - 1991)CHEVROLET(1979 - 1994)GMC(1981 - 1993)OLDSMOBILE(1979 - 1993)PONTIAC(1979 - 1994)