C.,
To find a reputable doctor that does sex selection is the first order of business. I tried it back in the 90's. I saw a doctor in Lathrup Village, but I don't recall the name. And it was not cheap and it came out of pocket.
There's always the method of when you ovulate, how often 'to', in order to improve a boy or girl chance. When I saw the sex selection doctor, I was given a script for Chlomid. That's supposed to enhance the environment, so to speak. What it did for me was create false hopes. I was on an emotinal roller coaster because it didn't seem to help and the disappointment sorta killed any further attempts. I didn't want to put myself through that. So I stuck with my 3 wonderful boys.