How can I ship an Ice Cream Cake to someone?

My friend doesn't have a perticular ice cream store in her area, and I want to send her a cake for a special occasion coming up. What is the best way to do this? I have no experience with dry ice...I don't even know where to get it, or how to handle it. Can I shipme something like this through the post office? Or another overnight service? Any advice woulde be helpful.