[Hacker]

I would definitiely shoot in RAW for the reasons stated above and set it to Auto WB. I'm surprised that no-one has mentioned that it is highly unlikely that you will be able to use flash inside a church, most of the God-squad don't like it and many of the guests will find it distracting.

If you do want to shoot weddings you will need to invest in some 'fast' glass, basically a lens with a very wide aperture (low f number). A good start would be a 50mm lens, either the f/1.8 or for a bit more money the f/1.4, my next choice would be the Nikon 17-55mm f/2.8 zoom but it is a lot more expensive (worth every penny though). I would also recommend a second body in case of failure etc.

Good luck with it and have a look at my site, all the church shots were done without using flash.