There are 3 (i think) nuts that hold the tank onto the bulkhead, then you have to loosen up the filler tube. Once you get the filler tube pulled off, it will seem like the tank is still stuck, just give it a few good tugs or pry behind the tabs that are over the bolts.
Be careful, you do not want to crack the tank.
Once it is loose, still with all the smaller hoses connected, follow Karl's guide for tipping it on it's side with the return line down and the filler hole up.
You may discover that the return line's grommet may also need to be replaced.