Go to the Veteran's Administration web site (VA.gov) and look up form VA40-1330. They will also have plenty of information to help you. You do need copies of his service record, death certificate, approval from the cemetery and patience. They really are interested in helping you with this. The SCV was helpful in pointing us to this and then at the memorial service for placing the marker they had a part in the ceremony. There are some significant fees involved, but these are noted on the VA web site. Free is the wrong term because there are costs involved in placing the markers. The low-cost placement option of the marker is for unmarked graves.
If the headstone is broken, it is best to have the stone repaired for historical reasons. Memorial marker companies often provide this service.
Overall, my experience in getting the VA to place a marker was not a bad experience. There was about $500 out of pocket expence, but the family paid the different fees including those charged by the particular cemetery.
Sam Vanderburg
p.s. I love this board!