As racer you have a total of eight events in which you must achieve a gold medal. I have the feeling that the events are compared to the main game a bit harder. I had especially at the event "Pushing the Envelope" difficulties. But I guess that with a little exercise are feasible. The eight events consist of ...
3 time trial
2 Hot Pursuit
1 Gauntlet (thx to Hanshiro)
During the eight events you can easily do the other Addon Achievements like the "Fender Bender", "Moon Shot", "Sting in the Tail", "Show of" and the "Slip and Slide"-Achievement.