its not a guarantee that it will work. i know for some hp models, they have a motherboard bios update that can be flashed to accept richland. i would research your specific laptop model and see what others have done, its likley been tried before.
why do you need the 5750m? do you need more power?
as long as you have a working 4600m you would be better off just getting the fastest ram you can get(maybe cas9 1600/1866 1.35v) and installing an ssd.