help -- my friends want me to make their wedding cake!

...and while that sounds like fun, it's also terrifying. I keep having visions of layers collapsing on top of each other during the ceremony. I've done a decent amount of baking, but nothing remotely so ambitious before.

tips? recipes? good books to read? any and all advice, cautions, recommendations and words of encouragement seriously welcomed.

It'll be for about 80 guests, and while I've been given artistic license, something vaguely traditional (tiered, elegant) will be expected.

thanks!