~~Sorry for the long message, but take the time to read through it...you'll thank me :)
I leveled from 1 to 70 as prot, and loved it. After 35, yea it does become fast. Having maxxed out Reckoning, Redoubt, and getting Blessing of Sanctuary...you are able to aoe grind. Aoe grinding is what makes prot a super fast leveling spec :).
Ret is nice for single target damage, and maybe even two. But with prot and the minimum talents (level 35 = lowest...which you are a nice chunk past that)...you are able to take between 5 and 10+ mobs at once, and finish in the time you could have killed two or three being ret..AND end up full on mana and health, without ever having to cast a heal.
At 55, which you said you were, I'd go with something near http://www.wowhead.com/?talent=sZV0tIx0zggooVb ...The mandatory talents to get (max) are Redoubt, Imp. Righteous fury, Reckoning, Blessing of Sanctuary, Holy Shield, and Imp. Holy Shield. All of those talents either make you block more, make you take damage when you block, or increase your health/decrease damage taken.
One-Handed Spec. is a nice increase of damage, but possibly not much at 55, but dont forget it is 10 % to every mob on you, if you have 10+ on you that all adds up to a lot of damage. Kings is a nice buff for others if there are two pallys in the group/raid/battleground, and also nice for yourself when tanking, but debatable until you max out your stats ((stam) at 70). Both talents in ret allow faster/lower mana judgements, which is very nice, and I'd recommend.
As for gear focus on stam and int gear because of a lack of spell damage/block rating gear around your level. Once your around 57 you can grab some spell damage plate (___of the sorcerer) off of the AH for pretty cheap..(TBC green drops)..Once past 60 keep your stam up, and get spell damage and block rating. More blocks = more damage done less damage taken...more spell damage = more damage. Don't worry about Attack power gear at all, less you have a few pieces left over. Your weapon will do less and less damage the more spell damage you get. And attack power doesnt effect most of your damage..which is coming from consecration, holy shield, your shield spike, and possibly judgement and seal of righteousness.
Grab a thorium shield spike, or any, from a blacksmith, and put it on your shield.
Most of your damage will be yellow...it will come from consecration, and blocking and having holy shield, blessing of sanctuary, and your shield spike proc. Getting hit soo often also makes redoubt and reckoning shine, and almost never not be up. Reckoning will allow your seal to hit crazily often, doing major damage, healing you frequently, or getting your mana back up for more consecrations.
For this prot aoe-style grinding you want to have a shield with a spike on it, blessing of sanctuary up, holy shield up as often as possible, consecration down when you can, and keep retribution aura up at all times.
If you are taking a lot of damage, judge and refresh light on yourself. Reckoning will make it proc pretty often, healing yourself, while all of your other spells/items/skills hurt the mobs from hitting you.
If you are running out of mana fast, but not taking a huge amount of damage, judge and refresh seal of wisdom. That will keep your mana up for holy shield and consecration.
If you are fine on mana and health, but maybe fighting an elite with 8 of his adds on you, or just not taking a lot of damage/using a lot of mana, judge crusader, and refresh seal of righteousness to hurt the elite/mobs a lot.
Feel free to use a mix of light and wisdom, along with righteousness when you can.
P.S. Use your mount to pull a nice number around 7...maybe more ..depends how hard they hit, and then fight them all on top of eachother, keeping them infront of you (so you can block)...This works best with melee, because you cant keep caster's bunched up, and their spells cant proc many of your main damage skills.
A nice place for you to try this out after you respec is north/east of the FP in western plaguelands...There are groups of melee undead, that are easy to round up, dont hit too hard, and your exorcism is able to hit them for added damage.
Good Luck with your new playstyle :P..hope ya like it :D