Unless you've got a very old model XXX - with the Bakelite motor (have never seen one taken apart myself - so don't know how those older ones are set up) - you should be able to merely remove the three nuts holding the entire motor assembly in the tank, and out it comes. Now, the rubber gasket/vibration damper boot may be stuck to the bulkhead, but should still come out with a little persuasion. If it's that stuck though - it may need to be replaced.
That is the only way I know of getting the motor assembly out of a XXX. After it's been removed, then you can service the brushes, bearings, fans, quite easily.
Rick
