Oh no... You're scaring me. I'm in the middle of planning a very complex wedding...and I'm a perfectionist.

First question: Do you want revenge or compensation? Both are valid answers but will determine how to proceed.

How far off-track did the wedding / reception go because of their failures? Did it run over time? Ignoring the car incident, did you incur extra costs because of it? How much were you short-changed? How wide-spread were these issues, such as the frozen cake? Was the frozen cake an issue for everyone or only some guests? What documents do you have from before the event which showed costs and/or promises made?

I'd start by asking for a detailed bill. No bill, no pay, or threaten a chargeback without a detailed bill. Then you can start dinging them on the line items where failures occurred. Remember, start high and negotiate down to what you're really wanting to get.

Back to the first question... if you want blood, hire an attorney. If you want compensation, start off with a reasonable number and good documentation on how you came up with that number. Ideally the number is big enough for you to be happy and small enough that they'll pay you to just go away.