Jsut clean it up, torque it to specs, and drive on. I usually pop the cap on the cylidner and push back the piston with a C clamp, but have not yet worked on these fancy arse 4 piston calipers.

Taking the caliper apart won't ruin it. It's putting it back together with improper torque that causes problems.

Here is a quote from the W123 Service Manual:

"Do not separate the two halves of the caliper since the fastening bolts are tightened to a definite torque by the manufacturer."

For the record, I never said that the caliper would be "ruined." What I did say was that the only safe thing to do with a disassembled caliper was to replace it.

And just what are the torque specs for the bolts that secure the caliper halves?