First, if they used any "real" guy's+armour in the updated SW yes, it was just older ROTJ stuff with some replacement part's. The "Seal" trooper's never did on screan stuff. What was done was one (and yes he may have been Seal) real US soldier was hired to do some "action" posses like run with weapon, hold/aim/fire with weapon, in general do some stand/sit/prone with rifle, as he was "filmed" for CGI stuff. You know when they glue the little white ball's at main point's on your body the get movement shot's for a program to play with. They CGI'ed a Clone Trooper over him, stuff like that. They made in the program big battle action shot's of the clone's fighting the Sep droid's