I agree with Dazzag that you shouldn't have to worry an extreme amount about your grades. For my 5.5 hour job interview last week they asked me what my GPA is, and that was it. They didn't ask what classes I did the best in, or what I had troubles with. They also didn't ask to see my transcripts-- you could technically say anything and it would be okay. Although I hear some programming companies ask for uni transcripts.
And be honest during the interviews. I was asked how my linear algebra was, and I said GREAT, because I actually thought it was something else entirely than what it is. I was lucky that they didn't ask for details. Later, during another interview with another programmer, he asked me how my matrix multiplication skills are. I was honest and told him that I never learned it in school but I am familiar with what they are useful for in 3D programming. He spent 10 minutes explaining what it was, then told me that it's called linear algebra and recommended I purchase a book about the topic. Looking back, if those original guys would have asked me a linear algebra question to solve, I would have bombed, and they would have caught me in a lie. (even though I didn't lie on purpose).
Anyways, yes, be honest. If you don't have the skills, be honest, as it's a lot better for them to say "come back when you know more about topic X" than for them to bust you in a lie and drag your reputation through the mud.
And yes, like Dazzag said, get a uni degree. There's nothing else like it, no matter how exciting the game design tech school courses sound. And study up on your linear algebra!
@svendetta - How did you make your XP look like that??
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