2005 E320 CDI is an SBC brake car, changing brake pads on it is not like other cars and the OP is lucky to have all fingers left.

If the correct tool to put the SBC into service mode is not available then there is a manual bypass that involves raising the car perfectly level, spinning a sequence of the wheels, rolling down the driver window and locking the car for 10 minutes to get (or something like that) to disable SBC. In this mode you can push the pistons back in.

To reenable the SBC there is another sequence which is then affirmed by the brake lamps flashing. This enables the SBC to advance the pistons out and the system tests by stopping each wheel as the mechanic turns it while on jacks.

OR

you use a scan tool to disable the SBC or remove the connector (which can make you require the MB scanner to reenable the SBC)

It is also mandatory for flushing the brake fluid.

basically its the same idea as if you are working on Toyota Prius/Lexus LS, LX or Land Cruiser brakes.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)