I've been asked to be the official photographer at a wedding, and I am both excited and terrified!

What should I do? I have no idea how to prepare for something like this and I am scared that I might botch it up and ruin the bridal couple's special day. On the other hand, I feel honoured and excited to take on the challenge.

I've been asked to give them a quote, but I have no idea how much I should charge, if at all.

I've made it clear that I have not done anything like this before.

Any tips or advice to this novice?