Try the FOI act, but you can also request information on your dad from the infromation provided on this weblink:
http://www.angelica.dds.nl/faqusarmy.htm
Also, call the local U.S. Marine Recruiting Office near you, or the Public Information Officer of the nearest Marine facility near you. They should be able to help. When you're able to track downthe specific unit he was in, you can contact the appropriate Regimental Association for more information. Good luck with your hunt. This was the approach I used to find out about my Dad's career in WWII and Korea. - Ed
Good luck with your search. It'll be worth all the trouble you go through in the end.
"There's no problem that can't be solved with a suitable application of high explosives"