Just a couple things:
1) WoW thread is basically dead, you should've probably just posted this here (not trying to be a dick, I bet it gets merged)
2) Levelling with a guild is best, especially a max level guild. They offer perks like extra exp, rep, some nice rewards, etc. Also with enough rep you can buy the heirloom stuff only available to guilds.
3) Levelling is piss-easy. You don't really need to buy new gear. Just go to the first Panda zone (I forget the name) and begin questing. You'll have enough gear halfway through your first level that you won't know what to do with it all. Seriously it's really easy, you could just take a dump on your keyboard and you'd be 90 in 3 days.
4) Add-ons. I prefer ElvUI. It's a pretty nice package that actually looks and functions really well. They always keep it updated, and I've used it since the beginning of WOTLK. Not sure how it looks on a shitty resolution, but I play at 1600x900 and it looks good.
5) People hate on this game a lot, so don't expect a mountain of advice. The game has turned into a very casual affair, and Looking For Raid makes it really easy to jump right in and go when you hit 90.
6) No idea what to spec as a mage, I'd assume any spec is viable now as I'm sure you've noticed that the talent overhaul significantly ez-moded up the talent trees.