I have an Eheim ECCO 2233 and all I do is unplug it and turn the valve to the "off" position on the intake hose. That is the most important. I forgot to turn the valve off once and I had about 10 gallons of water all over my carpet under the tank stand. 8O Of course, the filter was still plugged in so it just pumped water EVERYWHERE.
Once you that taken care of, just rinse your filter media in old tank water and put it all back together.