If your examaner is a half decent bloke/girl. than he/she is not out there to fail you.
If you are not sure about anything he asked, DO NOT MAKE IT UP. just say, "i am not sure but look it up for you in the poh.
finaly i have a question, Do you guys fly in and out off controlled airspace as i understand you do??
Why would you change to 121.5 to make a (pretent) maday call? why not do it on the tower frequentie?
And maybe before you sit the test go for a flight with an instructor in the 152, rather than have your 1st flight with the exam guy/girl.
there easy to fly just a bit lighter on the controls etc.
All the best with your test!!