While I'm not a 38B, I've looked into it quite a bit. I just submitted my reclass packet and awaiting a selection date. If you go to http://www.bragg.army.mil/sorb/ca/Pages/default.aspx
it will tell you all about CA.
There is a new brigade getting stood up so the need for a 38B is high. The 95th CA BDE is under SOCOM and the new 85th CA BDE falls under FORSCOM. From a friend of mine who just went through it all said that at the end of the selection course they have an additional try out for 95th BDE, if you don't do that you go to 85th BDE. All 95th BDE is at Fort Bragg, 85th BDE has a battalion at Ft. Hood, Ft. Bliss, Ft. Bragg, Ft. Stewart, and Ft. Lewis.
As far as being able to do SFAS, you can do it whenever you want. All you have to do is talk to a SF recruiter and get everything started. You can even do it from where you are now. I don't know how much 38B will prepare you for SFAS though I've been told that the selection course is based on SFAS, though not as hard and demanding. CA selection is only 10 days long.
Hope any of that helps. The site I gave you above gave me all the info I have and then gave me a way to contact the CA recruiters and they have helped out greatly asking all my questions.