Who are you using for the rest of the house? Are you subcontracting it yourself or using a general contractor? Do you already know what you want and how you want it? It really depends on what your needs are. If you already know what you want, where you want it, but need help bring it together in a efficient comfortable way, then just a designer would be of use and a general contractor to follow the plans. If you need help picking out everything, putting it all together in each room, then a Design/Build company would come in very handy. Good Luck!

It depends on the interior design firm you are looking for. When in doubt, check the portfolio on their website. That's a great indication of what a design firm is capable of achieving. Some interior design firms have millwork specialists as well as designers who are certified in kitchen and bath design. The great thing about hiring a designer specifically is that they have experience in combining a clients wants/needs with functionality to optimize the use of a space.