I'm glad you made it over to the HT board! I too felt there were some unsupportive comments on the other board. Welcome!
Anyways, as I said there, I believe it is your choice to do sex selection for a first child. It seems you have found a willing provider (doctor/clinic), so you are pursuing an available option. (Yes, I know some people fear that HT GS will lead to an unbalanced population. I think there are so few people doing it that overall it will make no difference.)
Yes, it would be great to be able to *avoid* GD. I understand your intent.
I think it's healthy that you are aware of your issues, and you take responsibility for how you feel.
I also hope your GC's pregnancy goes well, and that she has conceived a child of your desired sex.
I second the others that the maternal urine/blood tests are unreliable to diagnose fetal sex. I personally would not trust them.
As far as CVS or amnio on your GC to determine fetal sex... I'd say weigh the risks and how badly you need to know the baby's gender. If you need to test for health reasons (AMA, etc), that could be a factor too. If you *don't*, my advice would be to skip it. I guess it will also depend how your GC feels about having the procedure done. Interesting situation! :)
As far as some people not being okay with sex selection for a first child... don't let it get to you. Although everyone is entitled to their opinion, I personally believe some people are against it for reasons more to do with their own selves than anyone else's life. I hope this makes sense. lol
Bottom line is - you are doing what is right for you, what you are doing is legal and available, so I say go for it!
Again, GL with the pregnancy, keep us posted!!