I've just done this on mine I pumped the fuel out with a pneumatic pump thats just fed by compressed air and works with two diaphams
Another way of doing it use a vacuum cleaner to provide your suction in to a barrel
At the time I had no pump and someone had put petrol in the works diesel van so I dipped a pipe in the tank one in the barrel then another in the barrel and then to the vacuum hose a long way away (long hose required) the vacuum provides the vacuum in the barrel which pulls it out the tank.
Not sure how safe it is but i'm still here the best bet is the pneumatic pump or something like this
http://cgi.ebay.co.uk/DELUXE-SYPHON-...QQcmdZViewItem
Oh yea I pumped my fuel through a another filter in to a couple of cars