If you're going to sell it eventually, it'll probably be to another European. He'll be glad that it takes 230 volt so he doesn't have to replace the transformer himself or always use a step-up transformer. 8)
I don't know anybody who has done this, but I do know that it's as easy as unsoldeering the wires of the original one, putting the new transformer in place and soldeering the new in the same place where the old ones were. It's easy, every wire has its own color.
You can keep the original transformer and you can put it back easily in case you want to sell it to somebody in the USA or if you deceide to move there. :wink:
Chances are slim that somebody wants to trade your USA 115v TriAxis for his European 230v TriAxis, which is the intention of your post I think.