Hey Brook. Good luck tomorrow. I found Nav to be reasonably straight forward and if you read the questions very carefully you'll have no problems. Have alook at my post in this Nav thread for more details.
www.bobtait.com.au/forum/navigation/2063-exam-debrief
If you simply try and think about the following broad logic you'll be fine:
What is your required ground state ie: fuel and load etc
What is your required performance ie: fuel burn, ground speed, ROC
What is your track required, track made good, and drift
Be able to calculate x-winfd on the runway from TAF data
What are the positive fix points and methods of confirmation
What are the CTA steps, boundaries, and what are requirements to remain in CTA ie: 500' above the step, but step - 0 is OK for below the step
Be able to calculate the climb, descent rates required to maintain or stay outside CTA.
Know your 1 in 60s backwards and track error corrections.
What is the LMT and UTC ie; Arc to Time conversions at various times of the year - all in ERSA.
Know the Rhumb Line and Great Circle definitions
Know the BOD and EOD definitions and also what happens to these as you fly North or South; and East to West
I am sure there are other things but the main one is - RELAX.
If an old bugger like me can pass all these exams, a bloke like you will have no problems at all.