I shall add whatever knowledge I can conjure up to add to zircher's wise words.
As mentioned above, look at the demos, see what people have done. And for something on a professional level don't use Classic, go Pro, it just makes life easier, and prettier. The only reason to use DBC is so that even people with crummy computers could play it.
If you don't have any serious computer experience, you should hire a tech lead. This guy will tell what is possible and what is not, and how long it will take to accomplish certain things, etc. etc.
You will also need many artists, a writer, some audio engineers (including composers), and some others I can't remember right now.
There's also the thought on how to distribute it. Should you find a publisher? You will need to convince them that your game is good. Should you distribute it yourself through a web site? Chances are your game won't be very popular.
I guess the bottom line is:know what you're getting into. And try posting in the Team Requests Board for more success. I'd hate to see such an ambitious mind be flamed away.
Best of luck,
The Bear
Crazy Donut Productions, Current Project: KillZone
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