Get Mawhonic:
Just beat the last of the first four circuits in tournament mode.
Repairs:
During a race when you have damage Hold L2 + R2 to repair with no loss of speed
Unlock Sebulba:
To unlock Sebulba play as Anakin in tournament mode win every track in first place
Unlock Sebulba episode 1:
To unlock Sebulba episode1 pod play as Selbulba in tournament mode and finish every race in first place