Changing out the Z belt pulley

I noticed the Z pulley on the bottom of the Z belt has no teeth left. I have an extra pulley from a cannibalized machine but I am hoping I do not have to remove the entire spindle to replace the pulley. I see no other way to get the belt off the pulley other than loosening the Z truck. IS this the only way to replace the pulley? Thank you for any info you can give.

You do not have to take off the z truck. You have to release the tension on the belt by loosening the z motor screws and removing the Allen bolt - spring tensioner on top. The z motor will drop down taking the tension off of the belt.