Photographing a wedding! Tips, please?!

[Ivory_keys]

Hello, hello!
My aunt is getting married this weekend and asked me to take the pictures!
It's not a formal wedding at all, (they already got married at a courthouse), so they are just having an in-formal ceremony, so I don't really know what kind of photos she'll want me taking (i.e. pictures of them, pictures of guests, her getting ready, him getting ready, etc. etc.)
I just purchased my first DSLR camera (a Nikon D90), and it's being shipped to their place.
I only have a couple days to mess around with my new camera before the event (I'm played with my sisters D80, so i know a little bit about it, but not a ton), so i'm a little concerned as to how good the pictures will be.
So, I was wondering if anyone had any tips for photographing an informal wedding event, and any tips for my new camera?
I don't think my Aunt is expecting anything super fancy, just wants some cool pictures to have. I don't really know what she wants, though (haven't had a chance to chat with her yet.)
Any advice is appreciated.
Thanks so much!
-J.P.

Edit- I'm not willing to purchase any extra equipment, just what it comes with. I got it from costco, so you can see the list of the lens and such it comes with here