Car rolls down hill when in park? on 1990 Pontiac Bonneville

We have a 1967 GTO and I was wondering how hard is it to repair the parking pawl in the turbo 400 and what parts are neede

Asked by for the 1990 Pontiac Bonneville
I think the park pawl is in the extension housing. It might be a little messy but it shouldn't be too hard with a manual specifying how to adjust the pawl. If it's in the extension housing, you'll need that gasket and you might consider a new tail shaft seal while you're there.
Its the parking pawl about a hour to repair