...maybe you should bail out and live for another day.
.
Yeah, that was my first response when they asked me, but they insisted. They really don't have the budget for a "real" photographer. Their closer friend, the second photog, doesn't even have an SLR yet. He should be buying one any day, now 
You see how high priority pictures are on their list?
I'd post more pics so you could see something more representative of my flash work with PJ style portraits, but our staff doesn't like having their faces on the internet (law enforcement.)
Hey!
ooheadsoo, listen... if you bail out now believe me than you will bail out again on the next wedding.

I assumed that you've already said yes to them right? I do have a few questions I want to ask you.
1. Are you confident enough and believe that you can do this?
If yes, than go for it. Well, you have to start somewhere right? Even if you don't do wedding again than at least you will know what it like from this.
If it is an absolutely no than what else can I say, but back out from it. The sooner the better for them so they could find someone else on time for their wedding. But like I said before. If you bail out now than you will again.
2. Do they know that this is your first wedding gig?
If they know than they will also know the risk of having you doing this for them. Make sure you be honest with them and tell them that you are doing this the first time and the final photos might be as good as those pro, but you will do your best.
3. Have you show the couple your photos that you have taken so far?
This is very important part. Make sure you show them what you have done so far. And see if they are confident enough after that to have you as their main wedding photographer.
Wedding photography is not for everyone. It could be a long and grueling work. But at the same or sometime it could be fun to go. Once you get the hang of it you could actually hold a bottle of beer in one hand and shoot in another.
True that the responsibility is extremely high but as long as you are confident in yourself, your photo skill and careful this could be done.
Now it is time for you to decide for yourself if you ready for it. Good luck

Take care,
Buddy