These weren't really your fur-wearing crazy barbarians that you see in movies and TV shows. The Gothic soldiers perhaps were the least "tamed" section of Gothic society but the Goths were for the most part Romanized (they were Christian, respected their fellow Roman citizens, lived in peace with the Romans and their barbarian neighbors, lived by the rule of law). They did not trash things and pillage and massacre when they took over and occupied Italy (they were even "invited" by the Eastern Roman emperor). Their king Theodoric wanted to promote and preserve Roman culture (he had spent his youth in Constantinople). His reign was the most prosperous for Italy since the late 4th century, and he kept the Roman administration intact, since the Romans were better than the Goths at running a government. Also, there is no way to tell if a Roman or a Goth made those marks. It is believed that one or more hoards of 1st century coins were uncovered and taken to a mint or appropriated by an official and then revalued. These countermarked coins do definitely come from the Ostrogothic period (although some believe these actually come from the Vandal Kingdom in North Africa).
Centuries of contact and trade with Rome "civilized" the goths. When they first showed up in the 230's they lived up to the title of barbarian, they simply wanted to cart off as much wealth as they could for themselves.
Not documentaries on the goths, but terry jone's barbarians is a good documentary, but usually documentaries on the decline of the roman empire.