Any tips on photographing a wedding with my Nikon D40x?

The time of the wedding might be near sunset and I'm having some anxiety to whether its going to be hard to shoot with that kind of lighting. Do you have any tips? Perhaps an external flash?

Yeah an external flash would help so much. Check out the Nikkor lenses. You'll want a certain length of flash to put light on the subjects without washing out the beautiful background.

Here's a tip: If you have NO clue what you are doing bow out now and help the couple find an actual wedding photographer before you screw up their big day.

Keep in mind that flash use may disturb the ceremony, so find out at what time you would be permitted to do flash photography. However, the use of an external flash can produce acceptable results. So I would recommend an external flash for your D40x. Increasing ISO can boost the effectiveness of flash photography, along with a wide aperture (small/low f/number, i.e., f/2.8). I assume you are somewhat familiar with how to operate the camera, so I won't go in depth but, in flash photography the aperture affects the flash power required to arrive at the correct flash exposure. A wide aperture requires a lower power burst than a narrow one. So use aperture priority mode and select your widest aperture, and with a moderately high ISO (400-800) will increase an external flash's effectiveness. Also, drag your shutter a bit, nothing too dramatic but, a shutter speed of around 1/30 will let a little ambient light into the frame. Tip: Try not to get in the way of the photographer hired to shoot the wedding. There's nothing more irritating to a wedding photographer than an overzealous, DSLR toting family member. It's okay to squeeze in your shots, so don't think the photographer is going to have an attitude (although some may), just remember that he/she is being paid to shoot the event. Tip: Get in, take your shot, and move on. The pop of the flash will be noticeable, and can be annoying to the bridal party. In my opinion, faster lenses w/high ISO vs.a flash is the better choice during a ceremony.

To overcome anxiety, do some yoga. Wipe your camera clean before starting off (a confidence booster), keep reminding yourself that all great photographers were self-trained and Henry Cartier did all his photography with a 35 mm lens.
Go and blaze the trail… Conquer the the world of photography!