My (adult) medical consisted of:
a) Brief chat with doctor regarding medical history, any family illnesses and any previous hospital stays. They then examine you (check height, weight, BMI, tummy, lymph nodes, reflexes, eyesight, posture/straightness of spine)
b) Blood tests
c) Chest xray
Takes no more than 30 mins and they upload the docs directly onto immi.gov.au the next day if there are no problems, so you don't have to do anything. I believe your medical and PCC are valid for a year from date of issue.
Hope this helps