Hi Idovoodoo! Welcome to Wrong Planet! Check out the different forums and articles here. They are interesting and helpful. You are among friends here at WP!
I agree with Feralucci. I would like to add that you should not try to turn him into an extrovert. Most introverts are more comfortable being introverts. If left to our introversion, most of us will occasionally will come out of our "haven" to engage in a little bit of socializing, like for family occasions.
Also, don't spring sudden plans on him. It's best to keep to a routine, either rigid or loose, depending on his comfort level.
Because your son is of legal age and not living under your roof, you can't force him into any therapy. However, do give him some printed material about Asperger's and other spectrum disorders, and some links to stuff about it, too. Then it will be up to him. I am betting that once he sees how well he fits the traits in the info you give him, he will want to go deeper into it.
Don't forget to include the link to Wrong Planet in the info you give him. Enjoy the site! I do!
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If a man does not keep pace with his companions, perhaps it is because he hears a different drummer.
Let him step to the music which he hears, however measured, or far away.--Henry David Thoreau