A few suggestions for the wedding:

1) Have a duplicate (backup) for everything--that includes cameras, lenses, flashes, batteries, memory cards, etc.

2) Along the same lines, hire (or beg, borrow, or steal) a competent second photographer. Never try to shoot a wedding by yourself. There are too many vitally important moments during a wedding / wedding reception to risk having only one photographer. Plus, it works well when one photographer has a telephoto lens and the other a wide angle lens to capture two completely different perspectives of the same event.

3) If possible, scout out the ceremony / reception location ahead of time (assuming it's not terribly far away). Proper planning and preparation can make a significant difference on the big day.