This is a 97 with the switch blade key right? Where you insert an actual key into the lock?
This sounds like a jammed cylinder unfortunately.
There is a microswitch in the cylinder assembly that triggers the “take key” warning. It is tied into the drivers door switch. If your cylinder is stuck it is probably holding the switch in the “key in the lock” position.
Fortunately the 210 dashboard is not that hard to remove. I know when I took mine apart for the evaporator replacement the key switch assembly is its own piece. I do have the 98 with the Smart Key however. I am not sure how they handled the interlocking with the steering wheel on the pre 98 models with the blade key. I did not have to have the key inserted to remove the switch assembly from the steering column.
Official MB Video on how to disassemble various things, including the dash, on a W210:
https://youtu.be/Zdp4FDFJRcM
They really made the 210 easy to work on if you know the tricks. Just be slow and careful with the speaker grills in the dash, they are very easy to crack from years of baking in the sun.
One other thing, they do call for a special tool to remove the trim ring around the switch. It looks like the Rook in a chess set. It is available on the forum sponsor for about $30. If you don’t want to wait, you can improvise with two small screwdrivers, but be careful to avoid marring up the switch assembly or scratching the dash.