Remove positive battery cable, then pull the rubber cap back on the starter (driver's side, behind the IP) and remove the screw that holds the key wire and the large nut that holds the battery cable and buss wire.
You will have to jack up the car to remove starter -- on the 300D you can only reach the upper bolt from underneath while someone holds the socket on the bolt, but you may have more room on the 190.
Two bolts from the rear 19 mm I think, starter comes out the bottom.
Mine were STUCK, we had to use "foot power" on a 24" breaker bar to break the upper one loose.
installation was easy, except that the new starter had a different connector for the starter wire, had to clip the old one off and crip a new one on (supplied with starter). There isn't much wire to deal with.....
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!