My guess from your discussion is that the battery has died. Which lights dimmed when you tried to start the car?
Not being able to turn the engine over with the starter is a sign of a low battery charge, or a bad bendix.
Do any of the other dash/instrument lights light up when you turn the ignition on, or is it only the glow plug light that does not light up?
Diesels do not need the battery to run, so if the charging system is going bad, the car can run fine until you shut it off. This happens most frequently when you drive with the electrical stuff in the car running, like the blower motor, the lights and the other usual things in winter (rear window defroster, for example). All these accessories use the battery, but the engine does
not, so unless you notice the blower motor running slower, or the headlights dimming, you have no warning. You just find out you can't start it.
The most likely cause is worn brushes in the alternator, which come as a packaged part with the voltage regulator. The voltage regulator is on the backside of the alternator, and has an electrical connection (plug) that is held in by a wire spring clip and two screws. You have to pop the clip out of the way, then unscrew the two screws and kind of roll the voltage regulator out. If the brushes are less than around 3/8" long, they are shot. Others on this forum actually change the brushes (1/4" square cross section, 1 and 1/2 inch long graphite rods) alone. I have never done this and would spring for the voltage regulator.
If the brushes are unevenly worn, look at the wear surface. If it is rough and grooved, you need a rebuild. I would recommend you check FastLane.
Good Luck, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)