My son is currently undergoing genetic testing. The first test they did was the microarray and like the PPs said, it took about 3-4 weeks for results. Then, they decided to look further and they ordered a more specific genetic test and that one we are still waiting on - they said it would take 9-12 weeks.
As far as the actual genetics appointment goes, it is sort of like a physical, but more indepth. They really go over the child and their history with a fine-tooth comb. With my son, they saw things I never considered, like the soles of his feet rounded slightly outwards instead of inwards and his nose has a small cleft in it (which I thought was just a cute little trait he had and never considered as a "genetic marker"). The first appointment easily took about 2-3 hours.
Good luck! Genetics testing is a long process but it can provide a lot more answers.