There are six hex bolts on the front of the pump.  Four of these bolts are
the mounting bolts that hold the pump to the engine block.  You also need to
remove the two banjo fittings for the hydraulic lines to the pump; one on
the left side and one at the top.  When you have the pump off, you will need
a reseal kit with O-rings to repair the leak.  You will also need a new
gasket at the interface between the block and pump.  When you have the pump
off of the engine block, remove the remaining two hex bolts on the front of
the pump and disassemble it.  Install your reseal kit, reassemble the pump,
and reinstall to the engine block with the new gasket.  Check this link for
the gaskets and O-rings needed:

https://www.autohausaz.com/search/productx.aspx?sid=bqjzm155crrtzk2zxt0jdu55&mak
eid=800016@Mercedes&modelid=1195220@560SEC%20&year=1990&cid=hydraulic%20pump@hyd
raulic%20pump&gid=7540@Hydraulic%20Pump%20%20Gasket