For military records try the National Archives in St Louis. They will perform the research for you (for a fee) or you can schedule a time to visit and make copies. You need to give them info first (Name and military number) so they can determine if they have a file and pull the necessary items ahead of time https://www.archives.gov/personnel-records-center/military-personnel
Since today is veteran's day, many of the online databases are free. Try fold3 and findmypast.
Newspapers where your father lived are the most likely to have more general information. Reach out to the local genealogical society and ask them which ones are most relevant. You can then contact the local library if they are not digitized for assistance.