Do some research in magazines, regarding comparisons with lenses. These articles are very straight forward and frankly they pretty much tell the whole truth and nothing but the truth! You will get good information here on photo.net, and again not so good info.
My personal feeling is you are way under prepared gear wise. The cameras and lenses are fine for normal use, but I get the feeling you are trying to get out of spending money for PRO gear. You and your clients will both suffer because of this. I own 2 porsche cars and I would never think of taking the cars to jiffy lube, or hire someone for $8 and hour to replace the clutch with a Toyota part, therefore I don't think 3rd party lenses are the way to go, although there are some good ones made, but stay with Nikon, since thats what you own. The body, glass, and sensors are all setup to Nikons standards.
Can you shoot a wedding with your present gear? Of course you can. But at the same time you are doing a wedding and your gear can make and break a wedding.
Here is another example. I've seen wedding photographers show up in jeans. Even if the photos were ok most likely the bride and groom won't like them. You need to dress the part. A tux for evening weddings, and the finest gear you can score. If you need to barrow to buy on a credit card do it.
In the film days, before digital was out, almost all wedding professional photographer used medium format cameras, and most of them used Hassy's, Mamiya's, Bronica's, so forth. Showing up at a wedding carrying $20,000 to $30,000 was the norm. The negatives were at least 3 times or more the size of 35mm so you had much more room to enlarge prints with amazing quality.
With digital since you can see the pic and for some reason people think cheap priced cameras are OK for weddings. They aren't. They cannot compare to medium format. People can write to me all day long telling me how great their pics are, but it's not the same. Medium format will always win out. There of course exceptions with a few recent cameras, such as the Nikon D3 and the Canon 1Ds Mark 2 and 3. These 3 cameras actually approach medium quality cameras, but most pros still say medium format still beats out these $8000 DSLR cameras. So if you show up with $1000 worth of gear expect to see what you pay for.
2 lenses I feel are very good and with an upper end Nikon or Canom pro model are the 24-70 2.8 canon and the 28-70 2.8 Nikon. An added 17-50 is really all you need for weddings. If you want a fantastic portrait lens both the Nikon and Canon 85mm 1.2 or 1.4 prime lens is about the best setup for a professional wedding. Next is the 70-200 2.8 /vr /nikon or the 70-200 2.8 IS canon.
My last comment is simple. If you are charging the client money for your talent, time, and your gear 3 or 4 weddings will take care of most of your PRO gear, figuring $2000 per wedding, so think of investments for the future, not just a tool to get the 1/2 ass job done in a day.
My personal feeling is shoot THIS wedding with whatever gear you have. You will be just fine. And if this becomes an actual living for you, talk to your accountant a bank or 2 and start looking at the BIG picture. Get a loan with zero interest for 2 years. There are banks that offer it. I was just offered this through Bank of Americe, but my gear is paid for. If the say no, just 1 year only with zero interest take that too and soon you will find another card company offering 2 years. Just transfer the funds.
Since I don't know what your plans are keep it simple, but if you join the big leagues of wedding photographers have a blast. It's the best job one can have.