Talents for any class are important but for a Paladin as a Hybrid class they are even more critical. As a Hybrid class how you place your talent points determines what you can do, unlike a single purpose class like a rogue who no mater how they place their talent points they still are just there for damage. That just is not the case for a Paladin. If you put most of you points into the Protection tree then you are going to be a Tank, into the Holy tree and you will be a healer, and lastly if you put you points into the Retribution tree then you will be a damage dealer.
A very important thing to note about talents is that you can unlearn them if you need to. This allows you to build your character one way for early levels and then change mid-way or even late game to a different style. This is a general tip and works for all classes not just paladins.