Hi Ashieee,
from what I have been gathering, the procedures are like
this
1) Selection Assessment which includes:
i) Psychometric Test
ii) Physical Assessment
iii) Verification of Documents
2) Dialogue Session with the Assistant Director (Manpower)
3) A Psychologist Interview
4) A Panel Interview
5) Medical Checkup
6) Offer Letter
I do not know much about whether grades matter but I would think
it is more for your pay calculations and determination of your
entry rank. I think they depend heavily on the selection assessment
and also the activities that you have been heavily involved in to
determine your suitability.