Changing Power Steering Pump Filter

[Mike Belanger]

I have never changed this filter and after taking a look have decided that I have some questions.
Is the filter at the bottom of pump, therefore not visable when fluid level is full? Also which fluid line is the return? I would like to flush fluid and change the filter on my 1981 300SD.
Also I have discovered a vacume line that has been disconnected, it leaves the firewall, below the brake vacume assist and leads over towards the heater monovalve but ends without connecting to anything. Does anyone know where/what this line should connect to?

As always thanks for any help,
Mike.