My '87 Wolfsburg has a bad scrape (done by previous owner) along the
lower passenger side. It affects the base of the sliding door.

What questions should I ask when I take this in for an estimate?
Is there any well to tell a good body shop from a bad one?

Is this type of thing supposed to be fixed by fitting new panels, by
panelbeating or by filling in?
I have never had any bodywork done before so I am ignorant about this.