1989 Dodge Shadow broken half-shaft

I recently had the half-shaft on the passenger side replaced because it was making a lot of noise. I was told then that the driver's side could fail at any time. It began to make a noise every once in a while about a week later. Then while pulling out of my parking space, it made a terrible noise and the car stopped moving. I am assuming that the CV joint totally failed and I need to replace the half-shaft. Now my real question is this: When I pushed the car back into place, I noticed that even in park, the car does not hold. My parking space is on a incline, and it would not hold. I had to put blocks behind the back wheels. Is this to be expected when the driver side fails? Or, is there probably a further problem? I think I can replace the half-shaft, but if it is something more expensive than that, then I will probably replace the car. Thanks

Dave