Just bought a new Terrain, Elevation Edition and would like to change, for the winter the 19 inch tires to 17 inch and was wondering if this could be done.

I'm guessing this is the 2023 Terrain in your profile. Factory tire sizes:

235/50R19
225/60R18
225/65R17

You should be able to switch to 225/65R17 tires. They will be 0.7% taller, so you'll be going 1MPH faster than indicated when you get it up to an indicated 143MPH with a professional driver on a closed course.

To be sure, make sure you have more than an inch of clearance between the inner side of the rim and the tallest part of the brake caliper.

Welcome aboard!