Here is an alternate fluid exchange procedure I use for all my vehicles. You'll need a helper. The steps are rather simple.

1. Lift front tires off the ground.
2. Disconnect the ps return line, drain ps reservoir.
3. Plug open connection at the reservoir.
4. Secure the return line to a generously-sized container (at least one gallon). If needed, add a length of hose.
5. Fill reservoir.
6. Line up your bottles of new fluid for quick pouring.
Here comes the fun part...
7. Have helper turn car on, and immediately have him 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.
8. Button everything back up.
9. Clean up mess.
10. Top off fluid.

The front tires must be off the ground so the system is unloaded, otherwise a lot of fluid is pumped out with a lot of force. The return line must be secured to prevent a big mess. You'll probably use two quarts for this procedure. Make sure you have enough on hand. The helper must know what they are doing.

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95 E320 Cabriolet, 159K