I personally think that if you havent yet broken a horse, don't attempt it by yourself. Be sure you have another person with you (provided this person is hopefully well educated in training young horses).
I don't mean to say you can't do it, but im sure you'd rather it get done right and deal with the rough spots along the way, then have to deal with a half trained 1000pound animal, if you get what I'm saying.
Sorry if I'm not making any sense I'm so exaughsted EDIT-
Oh jeez. I completely went off-course, but basically the same applies for a ex-racer. Try it with someone whos experienced for the first couple times. You just need to remember that, that horse was trained to run.