You should be able to obtain your father's military service records, which may identify the decorations he was awarded or eligible to receive, plus provide details on his service. See this page: http://www.armed-guard.com/searchre.html, in particular the section entitled Researching Military Service Records.
You may be able to obtain replacement medals for any that he was awarded or should have been awarded. See http://www.archives.gov/veterans/military-service-records/replacement-medals.html
For your information, I have found records of your father at ancestry.com, a website more commonly used for genealogical research. In this case I found records of his arrival in New York City as a member of the Armed Guard detachment aboard SS JOHN SERGEANT on March 19, 1945, and again on May 29, 1945. On the first voyage the ship had sailed from Antwerp, Belgium, and on the second from Marseilles, France. He is listed as William F Dampman in March and as William Fred Dampman in May. I can send a list of the names of his crewmates to you if you like, although I would have no idea whether any of them are still living.
Ron Carlson, Webmaster
Armed Guard website www.armed-guard.com