What type of lens should I purchase?

I'm shooting a wedding in June of next year, I'm new to photography. I own a Nikon d3000 DSLR camera. I plan to do lots of reading on wedding photography and get advice from others but my concern at the moment is the type of lens. I'm not sure what lenses would be good for wedding photography. I have the 18-55 that came with the camera. I was wondering if I should consider a wide angle lens or a really good zoom lens and also is there a lens that offers both a good zoom and wide angle? Help? Thanks so much.

Added (1). Not as though I need to explain myself to you but its my sisters wedding. She isn't looking for a professional, as she already has one. I'm just there to catch things she may have other wise not gotten photos of, as photographers are not cheap. Anyway, for future answers… Unless you have something useful or helpful to say, navigate else where. I can do with out the negativity.

Before even addressing what lenses you might need, your first decision should be to figure out how to back out of the commitment. How is it that someone asked you to shoot their wedding when you are new to photography? Wedding photography is the most intense and demanding kind of photography. It involves all kinds of expectations that if you fail to fulfill can lead to ugliness. You need expensive lenses, external flashes, and a good camera. Then make sure you have backups of them all. Then have a year of interning or experience as a second shooter at real weddings.

Just to get you started, you need wide aperture wide angle, medium range, and telephoto lenses. The wide aperture is for the ceremony where the use of flash might be discouraged. There's just so much that you need to learn that you're inviting a world of hurt by taking this on.

I just shot a wedding not long ago for a friend of the family using a Nikon D90 with a 55-200 vr, sb-600, and a 35mm f/2. I've been doing photography for only 2 years and the only reason i did well at the wedding is because i had someone who had experience shooting weddings help direct my shots and cover for my lack of wide angle lenses with his own setup (i covered for his lack of flash). If you don't have someone shooting with you who is more experienced i would suggest trying to back out of the situation gently and explain you don't have the experience to do something like that yet. You can still shoot during the wedding but more as a guest then as a proper photographer. It is a very difficult thing to try just because of the knowledge in photography required to get results let alone set up shoots, organizing people, and directing/posing them.