Anyone can install gears but the good jobs well check and set the backlash properly. I do not know many shops that do this or even know how to do this.
So ask some questions when shopping around. I believe there is a place in St. Pete that specializes in just gears. I know Mike (4.6 Power) knows it but he is on vacation right now and I do not know if he is checking in.
PM him and ask.