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Gilly,

Thank you for your reply. Would removing the negative connection at the battery suffice as to "deactivate" the SBC system?

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If I were "forced" to do this job without SDS, I would certainly want to recommend disconnecting the battery, but Dr D is correct of course, that there is a pressure accumulator which is where the braking pressure actually originates from. The electric pump which charges the reservoir can't run without the battery power, but the original pressure would still exist. I don't think it's worth the risk, but it would at least somewhat reduce the risk of an accident if both batteries were disconnected.
I don't want to sound like an A-Hole here, but MOST 2003 E Class owners I would assume would have the car dealer serviced, for now. I too would tend to assume there is a problem with the SBC if the pads are worn out at 10,000 miles. If you screw up this job, it can hurt you and damage the car, and I'd HATE to see the (non-warranty) repair bill for THAT! New SBC calipers? Excuse me? Cha Ching!

Gilly