UI and Addons in general can make a huge difference for the game.
I would recommend trying Syiler's UI package that he built himself. You can find the information at
http://www.wowinterface.com/downloads/info22416-SyiUI-SyilerSyigamersUI-1920x1080.html
He explains exactly what addons are there with screenshots of how it looks and what you need to do to install it.
In the end, there wont be much that any addons or UIs can do to help you level, but they will make the game look nicer, and put some of the information in more easily recognizable places.
Once you are Max level, the addon known as Weak Auras is probably the most useful thing when getting to know a class.
There addon is very versatile and can make visual indicators for literally EVERYTHING a class can do. There will be people out there who have built packages for it to help others know about key abilities' availability, cool down, duration, proc, etc.
That's something to look at down the line though, as since you don't have most of the abilities until later, the addon wouldn't service you well.