2012 Subaru Impreza sedan: rear passenger window fell down

I have a 2012 Subaru Impreza, and the other day when I rolled the rear window down, it fell all the way down into the door. Safelite says that some piece of the regulator is broken, but they would need to replace a whole regulator. I haven't taken it to a real mechanic yet.

Problem is, I don't want to pay $500 to get the rear window fixed on a car I barely use. What I'm wondering is if there is a way to lock the window up (it's currently taped up) so that I can never roll it down again and just disconnect the motor.

Alternatively, I think I found the right part online. How hard would this be to do myself?