We're just trying to help. You should see some of the posts on here about wedding train wrecks.
So anyway, you've said you're gonna go for it... fair enough.
As someone mentioned, a couple external flashes may be good. Look for some diffusing things such as a softbox as well, probably at least one bounce card (though an index card usually works fairly well for this... also grab at least one of the "tupperware" style diffusers (white plastic) for whatever flash you wind up with.
Try to avoid using flash if you can, of course, but be wary of your depth of field and noise issues with higher iso if you go that route. (an app like neat image will help a lot with the noise but may soften the image so just beware)
EDIT: Clarification for above... depth of field isn't an ISO related issue.

I was rushing a bit. I meant if you're in low light, you're likely to use wider aperature, thus DOF may be a problem from time to time.
If you do go high iso tend towards overexposing just slightly as it works better on the properly exposed portions of the shot.
Bring an extra camera, SD card, etc. Rent a cam if you don't have a spare.
Good luck.