This is how I did it on the Milano. Can't imagine it would be much different on the 164, but I could be wrong so verify the procedure if you can.
Jack up the front of the car. Suck the fluid out of the reservoir, disconnect the rack return line (NOT the line from the reservoir to the pump) from the reservoir and plug the reservoir hole. Top up the reservoir with appropriate fluid and stick the open end of the return line into a jug.
Now have someone start the car and then turn the wheel back and forth. Stop the engine when the reservoir gets low (~10 seconds), top it off, and repeat until you only get clean fluid going into your jug. Put her back together and you're done.
Only thing to be careful of is not to run out of fluid in the reservoir. The fluid lubricates the pump, so running it dry would be bad. Also make sure you use the right fluid: some cars like the Milano use auto tranny fluid, and some use power steering fluid. Look in the manual for the 164.
If you have it, the white power steering reservoir supposedly has a replaceable filter. Probalby a good idea to replace that as well.
It is hose under car hooked to long U-shaped cooling tube located under driver's floor on LHD models. One hose goes back to reservoir and other comes from rack. Disconnect hoses from cooling tubing and let reservoir fluid drain out of disconnected hose. Now plug that hose to reservoir and refill reservoir with new ATF fluid. Now with other hose from rack open into a catch container in a drip pan start engine and cycle steering left and right to flush out old fluid. Be sure you keep reservoir full with clean fluid so you don't cavitate steering pump. Turn wheel full left and right to flush all old fluid out. Now you can shut off engine, reopen hose to reservoir and drain it and you are ready to remove rack. You will get some more fluid out of pump supply line from reservoir and pressure line from pump to rack when you unhook them.
Once you have the rack out inspect supply hose. pressure hose and hoses to cooling line. Watch out for two copper sealing washers on each of the banjo fittings when you remove hollow fluid bolts.