1st : pinpoint where the rattling is coming from...
2nd : If the rattling comes from door trim & speaker board, most probably can DIY and recitfy, probably a loose screw, pin, or gaps caused by normal ageing/wear & tear. Can be fixed one. My door trim had a slight gap near lower part of the door cos last time it got banged. Outside part was fixed nicely, but there was a dent on the inside. A quick and good mixture of epoxy putty made it silent till today.
3: If it's somewhere around the dashboard, still can DIY if u have the expertise and patience....both of which I'm lacking...especially the "expertise" part lah...if not sure I've instaled my black EG dash by now hehe