You need to contact a domain register company, speak with a professional. Get as much advice from other companies as you can. You need to hit up Yahoo and make sure the email is legit. If they sent you this warning email, by law you don't have to do anything really. It's only an email warning and they will use that against you in court for failure to comply if the email is legit. I saw you took down flickr-chicks.com already. Hope Yahoo is happy with what they got, i hope they give you some soft of exclusive Yahoo gift for the in convince they caused you over a silly simular domain name you owned.
Fuck you Yahoo, that's why i never use you or any of your owned sites for information, email and whatever the fuck else you have. I hope you burn with cyber karma!
PS. My fucking cock is huge.