First you have to get NTN (follow instructions at FBR website or call their helpline). It's very easy to become a filer. Download IT returns forms from FBR website. Declare your income. You can calculate the tax online. Submit the tax amount in NBP and go to IT office. They will issue you a stamped receipt and that is proof of your filing. When FBR updates it database your name will come up a filer when your CNIC number is fed into computer.
IT consultant fees vary from one lawyer to another depending upon the income being assessed. Call two three lawyers to get a feel of the market rate.