The rules about pet names and swear words have always been there. If at any point you have a question about a pet name you are interested in using, please file a ticket before creating the pet so that a staff member can give you a yay/nay on it. :)
Do file a ticket about the name change. Name changes under your circumstances (your username was taken while you were inactive) are supposed to be free, but sometimes the freebie expires. We'd be happy to gift you a free name change anyway, but you'll have to write in.