Hi there and congratulations on your upcoming baby. I have a daughter with DS who justed turned 2 in Nov. We didn't find out in advance and didn't test (because like you, it didn't matter, we would have had her anyway). She has been a delight to us and everyone that she comes into contact with. It is definitely an adventure with lots of ups and a few downs but lots of joy throughout. The best advice I can give you is to not read too much (it can be overwhelming) and establish connections thru the DSACF with other parents. They are going to give you the best guidance and support.
There is a play group that meets a few times a month where you can meet other parents with children under 5 w/DS and there is also a Mom's night out coming up in Jan where you can just sit and have dinner with other mom's without all the kids around and ask as many questions as you like. Great support from women who have been where you are now.
In regards to your question about financial help. There is a program that helps pay for therapy and other needs of children who are at risk. DS automatically qualifies your son for this program. To find out more you can contact the DSACF and ask them to put you in contact with someone from the Early Steps Program, I'll warn you in advance that it can be a little confusing at first but basically, its a program that will help until your child turns 3 yrs.
I am also pregnant, due in July. I know that pregnancy is a very emotional time and the news you received can sap some of the joy out of what should be a very happy time for you and your family. God has your little one in his hands and he will guide you through the journey that is to come and place people in your path that can help. Congratulations again on your little bundle of joy.
S.