Which lens should I use to shoot my first wedding?

I have a Nikon d300 and am shooting my first wedding on Sunday. I have an 18-55 mm lens and a 18-135 mm lens. I'm much more comfortable with the 135 but have read that the 55 will produce better images for the wedding. I will bring them both but which should I plan on using more and what should I definitely plan on using each for? Any any other tips for shooting a wedding? I have already compiled a shot list with the bride and think I know what to expect but would like to be as prepared as possible.

At a minimum you need a a 24-70 mm f/2.8 lens, but you should know this if you have done at a least one wedding working as an assistant. This is the MINIMUM experience you need to shoot a wedding. I will assume that you already have the necessary skills using the fine D300 shooting other assignments. It is up to YOU the photographer to assure that the price/quality (NOT quantity) ratio is excellent.

Formal wedding portraits are usually shot using a 50 mm f/1.8 or 85 mm f/1.8 lens

While these three lenses are what most wedding photographers carry with them, many also use a 70-200 mm f/2.8 lens when shooting candid shots during the reception and some of the photographers with the skills necessary to shoot the high end weddings ($5,000 and up before selling prints) use a lens like the 16-35 mm f/4 lens when shooting the wedding party during the dancing and other action found during a reception.

Since you do not have a backup camera, the 18-135 mm lens will be sufficient, since it covers what the 18-55 mm lens does plus more. Carrying the 18-55 mm would more like adding weight to your camera kit for no reason.

What you need to know when it comes to the business side of wedding photography

You have both lenses already, so would surely know if the 18-55 produces better images. If not, then do a quick test before Sunday.
No back up body? Reflectors, tripod, Two flash?
Rather you than me!

Dude, why have you got a semi-pro camera but entry level lenses? Use the 18-135 by the way, and be very careful with the ISO, those older camera's were bloody awful for that, when I was using a D200 I absolutely could not go over 400 ISO if I wanted my images to look acceptable.

The 18-55mm is all you will every need. Just stay as close as you can to the action!

None.

Unless you've worked as a second shooter for an established wedding photographer for 2 or 3 years you simply don't have the skill, equipment and experience required to photograph a wedding. You have 2 slow, variable aperture zoom lenses and neither of them are good for low-light/available light photography unless you really increase the ISO. You made no mention of what (if any) off-camera flash you have.

A wedding is a one time event. If you screw up the pictures and you're getting paid then expect to find yourself in court when the couple sue you for ruining their special day. Wedding photography is no place for the unskilled, inexperienced poorly equipped beginner photographer.

Swallow your pride and tell the couple to hire a professional wedding photographer.

If you screw up the pictures and you're getting paid then expect to find yourself in court when the couple sue you for ruining their special day.

You made no mention of what (if any) off-camera flash you have.