Stop discouraging greatness! If old Ben had of said "Gee, a rubber duck would be far easier to create than a device capable of harnessing electricity." than today we'd be using toothpaste powered light bulbs, or worse;
Munster cheese powered light bulbs, and that stuff stinks!
More to the point, AI's are as simple or complex as you want them to be. If you want an opponent's car to change direction at certain points in the track, I don't image it to be too difficult. And once you have the bare bones of the AI you can always add to it later. Most importantly, should you indeed find it too difficult to complete, you won't have wasted your time, you'll have attained more experience with the language and built a better assessment of what GM can/can't handle.
If people were to follow the advice often given "Don't attempt it, it's too hard" no one would ever get better at anything. I've made some pretty nifty games in GM by attempting. (and usually you'll find that with a bit of clever thinking, what you want can be achieved.
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