I had 2 glow plugs out on my OM606.910. The glow plug would come on after I started the car. It wouldn't stay on more than 30-45 seconds though.
You need to test them for resistance value to get an idea what you're up against. The intake seems daunting until you do it for the first time. Easy to do, just extra steps compared to an OM61x.......

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John