To ask "Is this the (last name) household? is (first name) there?":
(last name)-san no otaku desu ka. (first name)-san irasshaimasu ka.
it's hard to say what the response would be, especially if your friend isn't at home. As long as you got the right number, they would probably ask who you are (donata desu ka), to which you can respond "(your name) desu ga..." If your friend isn't at home and you want to ask them to email you, you could say.
ato de e-mail de renraku moraeru you ni otsutae negaemasu ka. (if they're older)
ato de e-mail wo okuru you ni tsutaete kudasai (if they're younger)
and just spell out the e-mail for them. Sorry, it's hard to guess much more at what could be said.