My first yorkie was a male
we got him when he was close to 6 months and had him neutered at 9 month and he didn't mark at all inside.
he's paper trained and pees like a girl.. he had the whole squatter style down! however he marks every 3rd post when we're outside.
If you guys really want a girl, i think you guys should wait! i waited almost 7 months for my little girl!