My first advice is for you to relax.

The MOST important thing a gifted youngster needs to succeed is a loving supportive home. I have also recently found out my DD was gifted and was nervous and anxious as well. One day my kid was normal and the next she was highly gifted.
What I am really looking for is someone knowledgeable and experienced to discuss how to best serve my son's needs.
No one knows your child like you! There is no one size fits all when it comes to gifted children so trust yourself above everyone else.
The first questions to ask is what sort of gifted program does your school offer? Does it seem like the sort of program your DS would benefit from? Is he happy in class or bored? Is he performing math and reading around grade level or is he grades ahead? Some highly gifted kids need lots of acceleration and stimulation and others, like my DD, are content with slowly analizing a concept and questioning the teacher like crazy? So far, my DD functions well in both her regular & gifted classes, but I am prepared if this changes.
My advice on the young scholars would be to wait a bit. It is a great program and yes IQ testing can be expensive. I think you should get your son settled into the gifted program at school. Once you have a better picture of what your sons needs are you can apply to YS and ask for help in the areas you think your school is falling short. It will help to add some school refrences in the YS application.
Do you have a gifted councelor or psycologist at your school? They are the best first resource to consult. I have learned alot from speaking with the councelors at my school. And this blog is an amazing support place.
Please keep us posted ...lots & hugs coming your way!