I have had horses for a long time (including babies) and have worked with weanlings and yearlings on several thoroughbred breeding farms (I live in Kentucky), This is going to be a process and if it doesn’t start out right lots of frustration for you, fear and lack of confidence for the baby. My best advice to you is to check out Pat Parelli. go to his website to get information. There is so much there as far as education, videos, etc. to get you and the horse started correctly. PLEASE check this out. I have been using these methods for years and I can tell you that if I knew in the past what I know now, many of my horses would have been happier and more confident (not to mention safer) and there would have been fewer tears on my part. As far as having the colt gelded that is just a must if you want him for a riding horse. You will need to check with your vet on this as you need to wait until both testicles have descended. Hope all works out for you.