My only concern for buying a used one (if that is what you were thinking) is that the first round of these may have had some issues. Mine, for instance, had a break in the wire located right at the motor. Seeing as that it never moved once since I put it in the tank, this seems like a manufacturing flaw. Also, the tech is the one that directed me to look there.
With a new one, you get full support. Used may not yield as much. At least get a proof of original purchase if you can...