Not sure if the National Guard would be considered active on the same level of signing up for a tour of duty, but it's worth a try. Was he ever deployed?
FF's right. The VA is the best source. You can look also for VA offices at your county or state level. They're staffed with service officers who are trained to help veterans and their families. If you have a VA close to you, you might also contact it and ask if there are VFW or American Legion or other service nonprofits with offices at the VA as they also provide assistance to veterans.
Our local VA has offices for these organizations right within the VA facility.
Our local VA has offices for these organizations right within the VA facility.
Good luck.