Based on my own experience with changing PS fluid, I wouldn't recommend the flush method described in several places on this board, including above. The PS pump goes through the fluid really fast and you have a really good chance of running the pump partially dry. What I have found that works really well in my opinion is to just disconnect the low-pressure hose at the reservoir, let the reservoir drain, suck out any remaining fluid in the reservoir with a MityVac, then connect the MityVac to the low-pressure hose and suck out any remaining fluid in the system. I think this removes most of the fluid from the system. After that you can replace the filter if there is one and refill the system. It's very important to bleed the system before starting the engine. Raise the front wheels and turn the wheels all the way to each side until the fluid level no longer drops in the reservoir. Then you can start the engine and repeat the wheel turning a few more times.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL