The National Archives has recently allowed e-mail requests for personnel records, but you have to be the veteran or next of kin to request records in this way.As a granddaughter unfortunately you are technically not next of kin. You'll need to download their form SF180 to complete your request.Your grandfather's WWII service number will be very helpful in locating these records.
Expect a long wait for these records (up to 6 months or more).
BTW, here's the info on your great uncle:
Laurent G. Fortin Technician 5th Class, U.S. Army service number: 31108038 29th Signal Company, 29th Infantry Division Entered the Service from: New Hampshire Died: August 1, 1944 Buried at: Plot H Row 23 Grave 34 Normandy American Cemetery St. Laurent-sur-Mer, France Awards: Silver Star, Purple Heart