How do I remove shower handle to change stem?
I'm assuming the screw you removed was behind the plastic/metal cap on the front of the handle. That handle has probably been on there since you were born and will have to be worked off. What has worked for me in the past is sliding a wrench behind the handle, over that chrome sleeve and tapping the back of the handle to try and move it forward. Continue to also move the handle back and forth. If all this fails, you'll probably have to get a small wheel puller to do the job.  Good luck