cabinet hinges
 

does anyone know of anyone who can swap out exposed hinges for concealed hinges on kitchen cabinets

This might not be practical, depending on the type of hinges that you want. The self closing type are typically installed in fairly precisely drilled holes in the cabinets and doors, which require custom bits.
If you are after "standard" hinges, you may find some that can be added just with screws, however, you will need to be very careful of the design of the door, especially if there is an offset such that the door is larger then the opening, the hinge needs to take care of this.
I hope you find what you are looking for, I am suggesting that you approach this and any contractor carefully, so you end up with a well done project. I think this is going to be more complicated then expected, IMHO.