Fix my form - repost

Hi, I need a form fixed. All the code is already there which I had another developer write for me so it should be a very small job. You will see on the page that there is already a form with three linked drop down categories that go -Parent --Child ---Grandchild and then there is a basic wordpress form with only a one level category.I need this form gone and the code with the three level category dropdown put in its place. When the form is posted,the grandchild categoryid is saved as the category in the database.