I'm only minorly familiar with the EIS on my 99 C230 parts car.

First think I'd do is remove the bolt from the steering column lock. This way if a total failure occurs you won't have to cut things apart.

I'm talking about the box on the left lower portion of column, under dash. Insert the key, wait for the ZZZttt noise of the column unlocking, remove the 10 mm headed nut then push the bolt up and out. This bolt is trapped when the column is locked. You can either zip tie around the box / column or pull it back and zip tie to something else. Be sure not to let the wires flex or be under strain.

Open the computer box on right side of under hood, near windshield. There should be a large purple ( color I think ) wire in a 8 or so wire connector that plugs into a rectangular relay that has 5 or so fuses on the top. Put a test light on this wire and turn key to start confirming that is the wire. With the key in the run position I'd apply 12V to the purple wire and see if the engine runs.