Yes, the power board is universal input voltage, because they cost engineered it down to a single part for world wide use, but the fuser assembly is a thin film resistor, carefully selected that it has a thermal time constant of a half second, so running on double the voltage likely will blow it up in under a quarter second, long before the thermal control loop has time to control it, and probably before the thermal fuse in there has had time to heat up. The ceramic heater is the only thing changed in converting between 120VC and 230VAC versions, the rest of the printer is otherwise identical. Power control for the heater is critical, as it has to come up to the right temperature in the half second it has between the printer accepting a print job, and the printer doing the raster conversion, and the coated paper arriving at the fuser assembly.
Older (as in ones that took 40 seconds of warming up before first page) had a single halogen lamp there, and these were often universal voltage, as the controller did phase angle control of the lamp to keep it at a dull heat, and kept it at close to fuse temperature all the time the printer was not in a sleep mode.
But yes, either use a autotransformer, not the cheap lightweight lamp dimmer style ones, but proper iron core and copper (or likely now CCA wire) windings, or simply buy a new printer on arrival, it will probably be cheaper than shipping the 120VAC model over.