It depends on whether you're talking about the original Hubble configuration or its current configuration.
First, Hubble does not have any thrusters, so it does not have propellant to unload (thrusters could throw particles around the telescope, affecting its view. Read more here)
Originally, the Hubble was designed to be returned via space shuttle, serviced, and then returned to orbit. To do this would require only the folding of the solar arrays and the capture of the telescope to be placed into the cargo bay securely.
Before returning the telescope, it would have to have some functionality in its pointing systems. This was so that it could be maneuvered to be grappled as well as due to heating concerns - if the telescope could not point itself for thermal control, then some parts may have been too cold to safely return to the much warmer Earth. See these requirements described here
Presuming it had this functionality, it would then have to have some things removed. This would take up to five spacewalks and even after this would have strained the shuttle's maximum weight to return.
The Hubble currently has enhanced solar arrays that would have to be removed, and a specialized cooling system for the NICMOS instrument (an IR camera that needs to be kept actively cooled) that can't be taken back to Earth because it is both too heavy and may not fit within the shuttle's cargo bay. Other than these two things, though, it appears that's about it, presuming that a vehicle existed to actually go and get it.