Just buy a manual. Someone has done this and if I remember correctly it cost him a few thousand bucks and it would have been cheaper to just trade the car in and buy a stick. You'll also have less problems going that route since the car came from the factory with a manual rather than have some shop put it in (and who knows whether the shop knows what they're doing). If you want a faster car, use the money to turbo what you have or trade it in for a faster car like a ralliart, Cobalt, SRT-4, evo, WRX, mazdaspeed3, etc.