According to Airservices, a GPS that meets TSO-C146a or later will meet the requirements for PBN. And According to the Australian AIP (Gen, 8.5.5.5) a TSO-C146A navigator will meet the requirements of RNAV 1, 2 & 5, RNP 1 & 2, RNAV APCH LNAV and RNAV APCH LP / LPV.
CAsA has a booklet that covers a lot of what you might need to understand, with some diagrams to assist your understanding.
Hope this helps, I'm still trying to get my head around it too!