I hacked into someone's facebook - And regret it.... Help ?

I was with my mates a few nights ago, and we were bored. So we decided to try and do it to someone, seemed like a great idea at the time. We didn't actually do anything once we were on there, just messaged one of our mates. We were on there for about 20 minutes and the person realised. They have contacted facebook and will find out my IP address. Should I just own up to it now ? I fear that her Dad may be quite annoyed with me as well though. And what about my mates? Should I say that they were involved?