Re: baby boy?
The sperm can last 3-5 days in a woman's body. The egg lasts 12-24 hours once it is released from the ovary. Usually, it is more likely that fertilization will occur with sperm that are present before the egg releases, though it is certainly possible that an egg is fertilized by sperm that come within that 12-24 hour window.
There has been some research that suggests that the sperm carrying the X chromosome (resulting in females), are slightly slower swimmers but are able to last longer in the woman's reproductive system, whereas sperm carrying the Y chromosome tend to be faster, but also die more quickly.
Therefore women who are monitoring their ovulation and want to conceive a girl often have intercourse a couple days before ovulation and avoid intercourse close to ovulation. It's vice versa for people trying to conceive boys.
This method was developed by Dr. Landrum Shettles.
This method is of course not 100% effective. It just changes the odds from 50-50, to 60-40 of one gender over the other. In the end what matters is that your baby is healthy and happy -- and so are you. But I can understand what it feels like to want one first -- for me the ideal situation is to have a girl first.
Anyway, I recommend reading Toni Wechsler’s book, “Taking Charge of Your Fertility.” It's got a wealth of information many of us should but do not know.