I have never had luck with any solvents removing lettering from stuff like this and not touching the paint (and trust me, I've used just about everything there is). Frankly, after all these years, I now firmly believe it just isn't possible to TOTALLY remove it without a trace.
I use the finest wet-dry sandpaper I can find and lightly sanding until it's gone, then dry-brushing like color in the same area. It's what some body shops used to do on painting of auto damage repairs a very long time ago.
Just kidding I'd probably say, do the best you can and paint over it. I think I remember a similar topic a few months back and the general consensus was that there would be no known way to remove lettering without affecting the paint.
Good luck though! If you find something that works, please tell us. I've got a few models of my own I'd like to re-letter.