2001 Mercury Sable Door repair

I'm not a body person, but you can get a body tool that may help you pull the dent out from the outside. It's a slide hammer with a small screw on it. You drill a small hole in outside of door, screw the tool in, use slide hammer to pull out the dent as much as possible. You may have to drill more than one hole. At the end you may need to use some body filler to smooth it out? Sand it, primer and paint it.

Another option may be to get a decent door from the salvage yard that will fit your vehicle.