Yeah, don't worry: there's going to be an extensive career code. Here's a preview article about it:
http://www.gamespot.com/xbox360/dri...clk=multimodule&tag=multimodule;picks;title;2
Here's what the official FAQ says:
How does the career mode work?
The career mode is a large number of events arranged in a pyramid. Competing in these events will earn you points and money. Points are the main driver of progress as new events and pyramid tiers will open up as you earn points. you will also unlock some cars this way. other cars (and alternative liveries for them) have to be purchased with money, and the amount of money your earn is dictated by the difficulty you compete at in each event. the difficulty is selected before each event, so players can set higher difficulties on what they consider thier specialisms to get more money, or set lower difficlties to pass events they may not be so good at.
What's different about Championship mode?
Championship mode is the "Pure Rally" part of DiRT. Cars that have been won or purchased in Career mode (of classes 4WD, FWD, RWD and Classic) can be used to compete in rally events at varying levels of difficulty and length. single rallies, short championships, and a full world championship are available, and each in an optional "short" or "long" format.