See if you can get a copy of Grim Fandango for the PC. It's a film noir mystery game set in the Mexican Land of the Dead.

The biggest problem I see with what you've proposed is that you haven't described what the moment-to-moment gameplay is like. What are the simple things that the player does over and over again? Is it just walking around and solving puzzles? Is there shooting? Is there fighting? How much of the game does each involve?

Good question Anynomuous poster, however I think I may be ditching the dectective game altogether and try something different. I was thinking of a 2d Active Time Battle type game (like Final Fantasy battles). I think I have a good storyline that would lend itself well to an ATB system.