It has been stated in different threads that if you delete your character in an attempt to remake it, you will not be able to. It will state the name is already in use. This is also the case in Queen's Blade. Perhaps in the future there will be a feature implemented that wipes names from the server, but right now that does not exist. I sincerely apologize.
As for guild names, I'm not entirely sure. I've heard that it's possible to change guild leadership but that may or may not be a rumor. I'm not sure, sorry!