Many people think using manual transmission on a rally game is difficult. Using it on this isn't bad. The majority of the time you can just work upto top gear and keep it in that. It's only on hairpins, sharp bends and collisions with walls and grassverges where you may have to change down a gear or two.
You don't need full points in the championship to get this, only finish in first place at the end.
I basically raced in the first championship (Aza Challenge in the Amateur league) with the Peugeot 206 WRC and with the off-road set-up.
Don't forget to change to manual transmission by going into settings when you choose your car. Use B to shift up and X to shift down.
Good Luck