I used NH since 2005. I did the first 2 Parelli levels, and then switched to Clinton Anderson- whom I like MUCH better.
When you purchase a Clinton Anderson kit, you get EVERY bit of information that you need to complete the kit and be 100 % successful! Fundamentals kit is worth it's weight in gold, and turns your horse from crazy to perfect! I have a half arab, and she's turned into a total GEM :)
I disliked Parelli since it purposefully leaves a lot of information out of the kits, and you as the student with lots of unanswered questions, in an attempt to make you have to buy more, pay for lessons, clinics, Parelli trainer etc. My horse was spooky, disrespectful & and downright dangerous when I was following their program...
I highly recommend Downunder Horsemanship- Clinton Anderson "FUndamentals" kit- it's what you need :)