I used to use his profession guides they really did help in the pre cata days (before WoW professions site was around) It's really up to you he does keeps his guides up to date and he does he homework (I still get emails) Their are some free leveling power leveling add ons to help you level much like the paid guides. Keep im mind I think he moved to a sub based plan and not a one time payment
The World of Warcraft API has a list of functions that you can interact with and to talk with WoW using Lua. These are your building blocks for manipulating WoW windows and chat boxes and so forth. Looking at these for the first time can be very daunting. But don't be discouraged. After getting more familiar with Lua the WoW API gets much easier, and the documentation gets much easier to read. Keep in mind there are many different ways to accomplish your goals, so when going though the API keep looking until you find a way that best suits what you need.