How challenging is Chopin's Prelude in C# Minor, Op. 45?

As far as physical technical difficulty it's not that much harder than the Rach C# prelude, but as far as phrasing and melodic line it is a tough little piece. But if you practice carefully I think you can nail it. Pay careful attention to all the accidentals and make sure you're bringing out the notes that need to be brought out (your teacher will help with that). Good luck!