Yes there are two different bus companies operating in Gregory Hills. Busways and Interline Bus Services. Buses go to Minto, Campbelltown, Leppington, Oran Park and Narellan
Yes, Gregory Hills Drive now connects you to Badgally Road in Campbelltown which also connects you to Campbelltown Railway Station. You also have convenient access the M5 via Eagle Vale Drive from Raby Road.