98 buick park ave. shakes n shifts hard and noises, is this a transmission sensor?

If the trans is original,13 years old, Iam
pretty sure your looking at a rebuild

You can have a trans shop address your concerns
and questions, but I doubt your going to resolve
noises and hard shifts with a sensor or two

You want to check the motor and trans axle mounts,
drive axles,etc also

Sounds like a trans mount when they go bad it causes all kinds of shakes , have someone put in gear ,open hood,, watch motor. tell them to hold brake and give it a little gas .Don;t stand in front of car .....see if motor raises up if so replace all mounts motor included. this is a common fix on theses cars.