Here is the procedure. You'll need a helper. The steps are rather simple.
1. Disconnect the return line, drain ps reservoir.
2. Plug open connection at the reservoir.
3. Secure the return line to a generously-sized container (at least one gallon). If needed, add a length of hose.
4. Fill reservoir.
5. Line up your bottles of new fluid for quick pouring.
Here comes the fun part...
6. Have helper turn car on, and immediately go through full range of steering motion (left and right) and shut off car, all the while you are trying to keep the reservoir filled.
7. Button everything back up.
8. Clean up mess.
9. Top off fluid.
A lot of fluid is pumped out quickly. The return line must be secured to prevent a big mess. Keep at least a gallon of ps fluid on hand. The helper must know what they are doing.
95 E320 Cabriolet, 131K