Meet the Oman

Hi all
First of all is it necessery to complete the mission Meet the Oman to finish the game?
The reason I ask is that after i met the Oman the first time and was escorted to their leader and given the test,of which i failed the first one i was not given the opertunity to do it again. I have tried to go back numeros times but they do not offer the test again.So I ask do I need to finish this mission it still shows as incomplete.??
Thanks in advance

The Canadian

That mission is necessary to complete the game. If you head back to Daru el Salam station (or whatever it was called), you should be able to find the training grounds again. They'll offer to test you again, and you'll be back in business.