The piece of loose metal looks to me like the broken end of the door check strap.

Most electric motors can be lubed and coaxed back into spinning. The hard part is that yours is probably soldered in. You c an fiddle with it once it is out by making a pair of test leads out of a nice long piece of 2-wire electrical wire and four alligator clips. These you hook to the battery to test the motor. If the armature is not burned and will turn freely, the problem could be that the motor needs brushes. You can fabricate theses. There is info about how to do this on this website. Do a search on motor brushes, replace brushes and such.

The usual cause of these not working is a lack of use. The grease seems to gum up after a decade or so. Lithium spray grease could be useful, as could WD-40 or some other penetrating oil. Make sure to lube it with real grease before you reinstall the motor. WD-40 evaporates. It is good only temporarily as a lube.

The window is attached to the regulator by a slide device. You might have to remove the rubber track and the bottom bolt of the triangular window to disconnect the window from the regulator.

I would remove the motor and fiddle with it first.

These motors are rather expensive, but you can find one pretty cheap if you look on the Web. If you go to a boneyard, it must be a driver's side rear motor. They are not interchangeable from side to side or front to rear.

Good luck!

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Semibodacious Transmogrifications a Specialty

1990 300D 2.5 Turbo sedan 171K (Rudolf)
1985 300D Turbo TD Wagon 219K (Remuda)

"Time flies like and arrow, yet fruit flies like a banana"
---Marx (Groucho)