Well i got my 550D this week, as well as my 17-85mm lens, and i am going to a wedding this weekend and have decided i may as well bring it along and give it a go. I am not the official photographer and they have hired professionals so it is not the end of the world if the photos do not turn out, i am doing this for my experience, so don't bother telling me wedding photography is hard, i have searched and found that out already.

Now my only lens is the 17-85mm, but i am looking at buying a 50mm F1.8 and a 55-250mm IS lens in the near future, would i be better off getting these sooner?

I only have the in built flash, will this be enough?

Lens hoods, i don't have any, should I?

I am pretty new at this should i just stick to Auto mode, or change it to one of the other auto settings, such as portrait mode or something? Or is this that moment where i need to take my training wheels off and learn more about depth of field so i can get some good background blur happening?

Any other tips for me?

Edit - Forgot to mention it is an indoor wedding!