Definitely.

The chains rarely snap, the issue is the plastic guides. I can’t believe she’s gone that long w/o a chain/guide replacement. If the plastic guides fail the chain jumps, destroys the valve train, and puts a nice hole in the valve cover. The failed guides can also break apart and fall in the sump. Not good.

The rough idle/stumble could be a vacuum or air leak. Check in the engine bay for broken, brittle, or loose vacuum lines. Check also for air leaks. Engines like ours use Bosch mechanical fuel injection/CIS, engine speed is increased with airflow, not an increase in fuel as with a carbed engine or electronic fuel injection. If too much air gets into the engine it will run rough at low speeds and at idle.

Replace all the fuses with brass/copper alloy fuses before you attempt to repair any electrical problems such as the window. Do not expect much in the way of fuel mileage, the issue is more of car weight rather then engine size.

These are the last of the big, beautiful, reliable, old school S Class cars. Enjoy.