OK, this looks like waaay too much work. Perhaps if I had a Mac everything would be very easy to do. And yet, I really think I’d rather wait for Apple to provide a way.
I don’t think Apple will allow other ringtones just by selling them. I really think they’ll let users create their own. And if they don’t — well, once they actually offer other ringtones, I’m sure the Brotherhood of Hackers will shortly thereafter deconstruct the steps so everyone can add their own.