No help with replacing the blower motor, but does yours make a whistling noise when the heat is cranked all the way up? Mine has since the car was new….

 

No problems like that,just a slight rattle on low speed and then get worse when the speed increases,think the blower is out of balance.

 

That does sound like an out of balance blower motor. I work for Mercedes as a technician and had a car come in for that a few weeks ago. My guess is that the blower motor is near the cabin air filter.