Most heirlooms only work in a limited level range in their default form and must be upgraded to work at higher levels. That costs gold, and you’ll need around 30,000 gold to outfit yourself with a fully upgraded set (counting only those that give you bonus experience). You may need to spend some time on a boosted character to acquire the gold you need to outfit another character with heirlooms, but it’s well worth the effort.
Before you begin, you must decide on whether or not to enable War Mode. War Mode makes it so that you will only see other players with War Mode enabled, which also enables PvP activity. Note that if you are in a party with someone not on War Mode while you are, you will be unable to see him or her. War Mode provides an experience buff as well as the enabling of three PvP talents that will greatly increase your power. Regardless of whether or not you enable War Mode, your objectives will remain the same in that you must complete all quest content to unlock flying later on and many of your War Campaign and Allied Race requirements. War Mode enables 10% bonus experience, 10% better rewards from World Quests, and allows for the gathering of Conquest points which can be used to buy gear. If you do play on War Mode, it is recommended to play with friends. Leveling without War Mode will not be significantly more time consuming.
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.