I am thinking about replacing the upper chain guides on my 400E. Does anyone know if a special tool is required to get the old ones off or is it an easy job?

I have heard stories about the plastic guides disintegrating, resulting in a jumped cam sprocket and possibly bent valves. I asked an experienced tech about this and he said that it was more common in the older engines, but he's never seen a 119 jump a sprocket. Has anyone seen this on a 119?

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles