Decursive is going to make your life as a healer oh so much easier. Make sure you get that immediately.
You can try healbot, or one of the other heal add-ons also. Can further simplify healing for you.
You might want to check out ArcHUD. Its pretty sweet once you get used to it. Shows your health, mana, enemies, etc as multicolored arcs around your character, so you dont have to take your eyes off the action.
I would get one of the taskbar type mods also, either fuBar or Titan Panel.
Actually, a friend of mine plays a tauren shaman and keeps a ui updated. Download this and try it out, lots of good stuff. A couple of shaman mods in there you dont need (like flextotem) but otherwise good for any class.
At lower levels the addons arent that big of a deal. At 60 and soon beyond, ctraid is essential if you raid. I love itemrack for one click change of armor, makes life easy. Titan panels are nifty for more info, I use the one for the top and bottom. Ive never played a healer, but decursive makes life easy.
Thanks for all the great ideas. I'll check them out when I get off work. Oh, and the server i'm on is 2 weeks old (blackwater) so everyone is about the same lvl. Got in on a guild at ground lvl. Loads of fun.