Does an Australian citizen without any German citizenship need any form of visa or anything aside from basic passport etc to travel and spend one week in Germany for business reasons?
Australian citizens do not need a visa for short visits to the Schengen area (including Germany), whether for business, tourism or any other purpose. However, you cannot work in Germany without a specific authorization.
I am not sure of the exact legal definitions but things like meeting clients, attending a trade-show, etc. are typically business activities while being employed by a German company to do something on site would be work.