There are LOTS of driving people in your area. Please go take some lessons with an experienced horse and driver combination before attempting to train your own youngster!
Green + green = black and blue as I'm sure you well know.
You can pick up many good safety tips from books and videos and if you're an experienced horseperson with good common sense and ability to read your horse's comfort level you can probably do a lot of the training yourself, but if you don't know what driving itself is supposed to feel like there's no way for you to show your horse how to do it.
That said, there's an awful lot of ground-training you can do yourself. Just how "untrained" is this youngster? And how old? If he or she is at least three, sensible, and has basic halter and lead training then you can be working on an iron-clad "whoa" and teaching ground-work and lunging. I cannot over-emphasize the importance of Whoa-Stand! Don't teach him to do it off a little jerk of the leadshank like so many mini people do, teach it as a voice command and hand signal so you can tell him to Whoa from anywhere in or out of his line of sight and he'll stop instantly. He or she should also know "Walk on," "Trot," "Trot on," "Back," and some version of "Step" or "Over" to indicate moving sideways. I personally teach "Canter" as well but that's an individual preference. The horse should be desensitized to barking dogs, rattling tarps, ropes in the vicinity of its legs, anything and everything you can think of. Bombproof is not too much to ask!
As for equipment, it would be good to buy a surcingle, maybe some elastic (or better yet, sliding) sidereins and a set of long-lines. You'll want to take lessons in how to use them but that's the basic stuff you can't live without. Well, that and an open bridle and a decent bit. Lots of threads on this forum about that!
Leia