Advice needed from you veteran Healing Priest out there
When I first started playing WoW years ago I started with a Rogue. It was ok during Vanilla, BC, and part of WOTLK. I then rolled a DK and started tanking in WOTLK up until now. During the middle of WOTLK I rolled a priest and got it to 80 then put that toon I ice for a long time. When Cata dropped I continued Tanking and decided to roll out a Mage alt and feral druid alt. During the last 3 weeks of 4.2 I started playing my Priest again for the first time in a year. Shadow was the way I went because I decided I didn't like the stress that healers went through during raids. Then I decided to be brave and started getting gear to be a healer. Hell, I really enjoy it now more than tanking. I now understand the pressure healers go through in 5-mans and raids.
Take a look at where I sit now and give me some words of wisdom for you much better healers out there. I decided to go Disc as my main spec and found holy is good for certain boss fights in DS. I have done the LFR which we know is more easier than normal mode and I have done normal mode in DS but only made it pass the first boss. Now I have read through alot of information on Priest on this site and others to learn as much as I can. I have also found asking through MMO Champions has helped me in the past with my other toons. So, lay whatever you think on me.
At your gear levels, you can get rid of a good chunk of spirit. 3k is overkill for disc, as you should be able to keep your mana up fine with proper use of rapture/cd's at 2500 or so spirit. Reforge what you can to crit/mastery until you get a good enough hang of mana regen mechanics to switch to haste/crit. It might be a good option at the begining to replace that chest with the JP t12 chest for the 2p, as it is very good mana regen without relying on spirit.
Your Priest looks good!
Keep in mind that Int is King for Disc hands down.
Change out your Zen Dream Emerald gems to Int/+Spirit if you are going for socket bonus. Also, take a look at even going all Int Gems if bonus is just +10.
Like Luctus said, you can offered to reforge some Spirit, (or change gems) especially with using Tsunami and Core.