Remove the door panal and take a look. On the W126 they come off in about three minutes once you know where the screws are.

http://catalog.peachparts.com/RenderScriptTemplate.epc?_cmd=epccat_VehicleAAA&cookieID=2G510NISS2G510NUMK&yearid=1991%40%401991&makeid=MB%40%40MB%40%40X&modelid=350%2DSDL%2D001%40%40350SDL&catid=O%40%40Body+Mechanical+%26+Trim&mode=PA&subcatid=O3044@@Window+Regulator+Roller&source=www.peachparts.com&clientid=catalog.mercedesshop

Mine just needed this...

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200