You need to get an FHA consultant first, to inspect the house once you have a contract and then shop for the contractor...the consultant determines what has to be done with FHA funds and then you if there is anything else you want to do, you can. Are you doing a streamlined loan of less $35000. Do you have a lender and have you found a house yet and is it under contract, if so I have a contractor who is approved for FHA 203K out of Elmhurst. Your lender should be able to also give you names.
Jolyn's answer is correct. I just wanted to specify that you need to use "approved" contractors from the 203K program. In some instances you can use someone that hasn't yet been "approved" yet they need to go through the process and be "approved" before they can begin work on the home. Best of Luck!