I am going to buy a 1998 E320 and the current owner says that he is selling it because the key won't turn.(I assume this is the W210 chassis)

He said that it did this once before but eventually worked.

Now, it's just stuck he says.

He also told me that the ignition switch it needs from Mercedes is $900.

Is this right?

I see ignition switches for this car online for anywhere from $40 to $90.

Also, assuming this is the right part, do any of you know how hard is it to repair/replace this switch on this car?

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1993 W124 300D
-297K on the clock as I type this.