when I put my car into park it slips and doesn't engage into park properly. on 2000 Saturn SC1

I'm afraid that when I park on a hill the emergency brake might fail and the car will roll away. isn't the transmission supposed to lock when you put the car in park. How much does this cost to fix?

Asked by for the 2000 Saturn SC1
seek a free diag and est from aamco then shop prices