It seems, at least on my opinion, that the retri pvp spec is more powerful that this one, as in, the pvp spec gives more advantages to pvp than the pve spec gives to pve. i had to put some talents into long arm of the law or guardian's favor simply because they were nowehere else to be put. long arm of the law is useful when you need to move away from the boss for a while, then get back as quick as possible for example.
guardian's favor is not very useful. it just decreases cd of hand of prot, which is swell if you find yourself in the position to save your healer, and that's about it. maybe eye for an eye is better, but, i assume it may cause threat at some points when you don't want it. still, it is a bit undecided here.
As to how to play, the same as in pvp, except that you also have divine storm to consume your holy power on, and, obviously, you should use it when you have multiple targets, together with the seal of righteuosness which hits multiple targets (recommended talent point in my pve spec). for single targets, spam templar's verdict as mentioned above.