The best place to start is here:
http://www.archives.gov/veterans/military-service-records/standard-form-180.html
Veterans or next-of-kin of deceased veterans can use the online order form at vetrecs.archives.gov (or use the SF-180) to request military records.
I used this to find out about where and when my father served. Great service and fast results even though it is from the government. :-)
You can do it all online and they will email you when the information is in the mail so you can have the paperwork.
Once he has this information he can search dates better and places, types of jobs, etc.
The biggest roadblock I hit when looking into my own Father's war record was being informed, when I requested a copy of his service record, that it and millions of others stored in a St. Louis archive were destroyed by a fire some time in the 1970's. That should never have happened.
I know you posted the info back in December, but thanks for the info on requesting records.
I got documents of my Dad’s service in WWII - but not organized.