[need to know linden rules on performing weddings]

Nope. Because there is nothing "Legal" in the firt place about Partnering or holding a wedding ceremony for avatars.

Designating someone as your SL Partner does only one thing - it puts the partner's name in the other perspn's profile as their Partner. It conveys no other rights or privileges.

Holding a wedding ceremony in a virtual world also carries absolutely no legal significance, so anyone could do it, in any way they choose. It means nothing legally.