I covered my first wedding last June, having been asked to do so by my girlfriend's sister, who was the bride. I thought my coverage of the wedding would amount to a decent wedding gift. I used the Rebel XT and - yes, it is true - the kit lens, which, to state it mildly, does not at all compare favorably with my current choice in lenses. I had no back up gear with me, because then I had no clue whatsoever of what a wedding photog needs and how to cover a wedding. While the results of the coverage didn't turn out to be the absolute disaster, I would encourage you - strongly encourage you - not to rush in where angels fear to tread. As a matter of fact, I just recently turned down an offer to cover a church wedding, because I lack the experience, mine being confined to covering town hall weddings in my community. Don't rush in, despite your belief in your own talent, maybe try the second shooter option. A church wedding is a very - very! - major event in the life of those getting wed, don't provide the couple with images that, when they look at them in their mutual days to come, will leave them disappointed. And really, forget about the Rebel XT, toss the idea into the wind and invest in a more sophisticated cam and especially fast glass. I didn't want to sound like a jerk in this message, just wouldn't want you to crash like Icarus.
Greetings from D.