From what I understand, in a method similar to Genghis Kahn, the German tribes came south and progressively destroyed everything in their path as they travelled down the Italian Peninsula, eventually even destroying the city of Rome itself. From what I understand, it was also in these attacks that many texts, documents, and works of knowledge were destroyed in these attacks and lost forever. And then they left, leaving the Romans to fend for themselves among the ruins of their old societies.
What I mainly want to know is how did the Italian(Roman) people who survived these attacks react? They were a people who had, at the time, some of the highest quality of life on the planet. How did they react to such a dramatic change? How did they change? How did their lives and the structures of their communities change? Many works from this period were destroyed, and during the Dark Ages that followed few new works were created, so any links to sources and original documents would be greatly appreciated?
Your understanding is incorrect. The Germanic tribes did not 'destroy everything in their path', and they certainly didn't 'destroy Rome'. Rome was occupied by German armies twice, but the city was most certainly still standing afterwards. The Germans also didn't just raid and leave - they stayed. And by stayed, I should point out that many of them had been living in Italy for years already as former members of the Roman army given land in compensation for their service. The final 'end' of the western Roman Empire had as much the character of an internal coup as it did an external invasion. The Germans didn't want to tear the Roman Empire or Roman society to pieces, they wanted to lead it themselves.
As an aside, the Mongols didn't do what you described either - they did sack cities that refused to submit to them, but this was done as a negotiating tactic (albeit a very brutal one), they didn't simply sack and destroy everything they encountered.