How To Pick Out The Horse For Me?

My grandfather owns a farm and several horses, all who are granddaughters/grandsons of Beau's My Daddy, meaning they are all well-bred horses. He said I'm allowed to have any of them, as long as they are over the age of 5-7. None are trained yet, but we will be paying for the training. Should I allow a horse expert to pick out a horse for me, and should I do it myself? I have little experience, but often get those "perfect horse" connections. I did with my last horse, Dazzle, who caught a sudden case of moon blindness and needed to be put to sleep. He was the best. (: So should I do it, or have someone experienced do it for me? Thank you!