Yup Raiding is for groups of 10 or 25 people, dungeons are 5 man teams.
There is 2 differences between a Protection Paladin and a Retribution Paladin.
The first is in the talent points you spend. One talent build is designed to increase your "threat" which basically means the increase in chances of the mobs you are attacking, attacking you. This is good for tanking. The other thing the talent points should do is increase your health and armor. In retribution, you will want to be increasing damage but lowering threat so you dont pull mobs onto you.
As you have probably worked out by now, the different stats do different things for you and can do extra things (like add spell damage, depending on your talent build).
The basic stats are:
Stamina: Increases Health.
Intellect: Increases Mana Pool and Spell Critical Strike Rating.
Spirit: Increases your MP5, which is your mana regeneration over 5 seconds.
Agility: For some classes increases DPS but also dodge rating, or how likely you are to dodge an attack.
Strength: This affects how hard you hit with a melee or ranged weapon.
Attack Power: This directly affects Melee and Ranged physical damage.
Spell Power: This affects Spell damage.
Defense rating: There are different defense "caps", the "cap" means that mobs X levels above you cannot crit you which reduces damage you take enormously.
As a Tank (Protection), the most important stats are Stamina, Defense Rating and at level 80 Parry and Block.
As DPS (Retribution), the most important stats are Str > Crit > Stam > Int > MP5.
HTH, Any other question's ask away