I agree with invictious, that there are certainly easier Polonaises than the "Heroic" to start with! I find the "Military" Polonaise (Op. 40 no. 1) fairly easy and quite a good piece, if played properly.
And my teacher always insists that I start working on a piece SLOWLY, getting all the notes AND PHRASING correct, before trying to play at tempo. With the bigger pieces like the Polonaises, it is essential to NOT develop bad habits at first or the pieces may never sound right.
Good Luck,
Bruce