Modify Small PHP Form in Joomla Website Urgent

Hi, We have a php form for collecting the email address & name from visitors. We'd like to add the following fields: -Postal address -Phone number -A collection of checkboxes with the question "I am interested in:" * Farm stay activities and animals * Organic food and wine * World Heritage National Park / walks * Nature retreat * Horse riding, kayaking, 4WD, mountain biking * Massage and beauty treatments * Exclusivity team building / conference -Dropdown box for "How Did You Find Us" We need this done pretty quickly. We'd prefer someone who can work during AEST between 8AM & 7PM in case there are any questions. Lee.