1st Serg sent a admin separation request on my son and he has been diagnosed with PTSD (on base). What happens?

My son has been in the USMC for 3 years active duty. He has not had the cleanest record (under age drinking, etc.) he has been NJP'd. His 1st Serg sent a request for Admin Separation (the serg is no longer there, been reassigned) but the paperwork is processing. His NJP was durring his 1st year of service. He did not know he was sent up for administrative separation, until his new Gunny told him he received a notice today about the separation where they asked his opinion on my son and he said he would go to bat for him. He has been great since he has been back from his tour in Feb 2011 no trouble. He does not want to be separated and wants to fulfill his obligation. He does not know what to do (change of command, says he can't go talk to anyone).To top it off... they sent him to medical TODAY and diagnosed him with PTSD which they originally said he did not have. He received his Combat Ribbon while in Afghanistan. What should he do? My son is very smart but went straight in after high school and thought he was a bad a$$ and yes he was no angel but he is trying hard now. He does not even go out on weekends with his friends so he can stay out of trouble. I am scared he will get an OTH, and he will lose his GI Bill. He walked away from 2 full tuition scholarships for college from high school to join the military. All this and he is not even 21 yet.