Blower make a noise when climate control is on auto. When I stop noise stops. on 2007 Mercedes-Benz CLS550

When climate control off, no noise. Thoughts? How difficault is it to replace blower motor?

Asked by for the 2007 Mercedes-Benz CLS550
its a 1hr job and poss there is debry inside fan blades or a bad blower motor itself
Thanks, any directions or instuctions how to remove it?